Note: Descriptions are shown in the official language in which they were submitted.
~ ;~3~6~2~
MAGNETIC TRANSDUCER HEAD
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic transducer head
and more particularly to a so-called composite type magnetic
transducer head in which head portion in the vicinity of the
magnetic gap is formed by the ferromagnetic metal thin film
or films.
2. Description of the Prior Art
With the recent tendency towards increasing the signal
recording density on the magnetic tape used for VTRs (video
tape recorders), so-called metal magnetic tapes in which
powders of ferromagnetic metal such as Fe, Co or Ni are used
as magnetic powders for the recording medium, or so-called
metallized tapes in which the ferromagnetic metal material is
deposited in vacuum on the base film, are used in increasing
numbers. The magnetic material of the magnetic transducer
head employed for signal recording and reproduction is
required to have a high saturation magnetic flux density Bs
in order to cope with the high coercive force Hc of the
recording media described above. With the ferrite material
predominantly used as the head material, the saturation
magnetic flux density Bs is rather low, while the Permalloy
presents a problem in that it has a lower wear resistance.
With the above described tendency towards increasing
346~6
the signal recording density, it is more preferred to make
use of the narrow track width of the magnetic recordlng
medium and hence the magnetic transducer head is required to
have a correspondingly narrow recording track width.
In order to meet such requirements, a composite type
magnetic transducer head is known in the art in which the
ferromagnetic metal thin film having high saturation flux
den~ity is applied on the non-magnetic substrate e.g. of
ceramics so as to be used as the recording track portion of
the magnetic tape. The magnetic transducer head however
presents a high magnetic reluctance because the path of
magnetic flux ~is formed only by the ferromagnetic metal film
of a reduced film thickness so that the operating efficiency
is correspondingly lowered. In addition, an extremely time
consuming operation is involved in the manufacture of the
magnetic transducer head because the physical vapor deposi-
tion with extremely low film-forming speed are necessarily
employed for the formation of the ferromagnetic metal thin
films.
A composite type magnetic transducer head is also known
in the art in which the magnetic core elements are formed of
ferromagnetic oxides such as ferrite and the ferromagnetic
metal thin films are applied to the magnetic gap forming
surface of these core elements. However, the path of magnetic
flux and the metal thin film are disposed at right angles with
-- 2
123~6
each other and hence the reproduction output may be lowered
due to the resulting eddy current loss. Also a pseudo gap
is formed between the ferrite magnetic core and the metal
thin film thus detracting from the operational reliability.
Summary of the Invention
It is therefore a principal object of the present
invention to overcome the above described deficiency of the
prior art and to provide a composite type magnetic trans-
ducer head consisting of the ferromagnetic oxide and the
ferromagnetic metal thin films, which is improved in molten
glass fluidity, bonding properties and relaxation in the
internal stress, and which is free from deterioration in the
ferromagnetic metal thin film or ferromagnetic oxides, crack,
breakage, erosion or bubbles in the glass fillers.
With the foregoing object in view, the present inven-
tion resides in a magnetic transducer head in which the
magnetic core elements of ferromagnetic oxides are sliced
obliquely across the junction surface of the core elements,
ferromagnetic metal thin films are formed on the resulting
inclined surfaces by employing a physical vapor deposition,
and the core elements are placed with the respective ferro-
magnetic metal thin films abutting to each other for
defining a magnetic gap therebetween, wherein the improvement
consists in that said inclined surfaces with the ferromagnetic
metal thin films formed thereon are inclined at a preset
3~
angle with the magnetic gap forming surface, in that non-
magnetic films having high-hardness are interposed between
the ferromagnetic oxide and the ferromagnetic metal ~hin
films, and in that said ferromagnetic metal thin fllms and
the oxide glass fillers and provided on the tape abutment
surface by the intermediary of the non-magnetic film having
high-hardness.
The provision of the non-magnetic film having
high-hardness between the ferromagnetic oxide and the
ferromagnetic metal thin film is effective to inhibit the
reaction otherwise occurring between the oxide and the
films, while positively preventing the formation of the
boundary layer with inferior magnetic properties.
Likewise, the provision of the non-magnetic film
having high-hardness between the ferromagnetic metal thin
film and the oxide glass is effective to prevent the erosion
of the film by the molten glass, while also improving the
molten glass fluidity.
Brief Description of the Drawings
Fig. 1 is a perspective view showing an embodiment
of the magnetic transducer head according to the present
invention.
Fig. 2 is a plan view showing the contact surface
thereof with the magnetic tape.
Fig. 3 is a perspective view showing the magnetic
~23~6;~
transcuder head shown in Fig. 1, with the head explocled
along the magnetic gap surface.
Fig. 4 is a plan view showing the contact surface with
the magnetic tape and especially showing the construction of
the non-magnetic film having high-hardness.
Fig. 5 shows in perspective a preferred construction
of the magnetic transducer head in which the non-magnetic
films having high-hardness are provided only on the
interface between the ferromagnetic oxide and the ferro-
magnetic metal thin films and Fig. 6 shows in perspective
a preferred construction of the magnetic transducer head
in which the non-magnetic films having high-hardness are
provided only on the interface between the ferromagnetic
metal thin films and the oxide glass.
Fig. 7 to 14 are diagrammatic perspective views
showing the manufacture process for the magnetic transducer
head shown in Fig. 1, wherein Fig. 7 shows the step of
forming a first series of grooves, Fig. 8 the step of forming
the non-magnetic film having high-hardness, Fig. 9 the step
of forming the ferromagnetic metal thin film, Fig. 10 the
step of forming the non-magnetic film having high-hardness,
Fig. 11 the step of charging molten glass filler and the
surface grinding step, Fig. 12 the step of forming a second
series of grooves, Fig. 13 the step of forming the winding
slot, and Fig. 14 the step of melt bonding or glass bonding.
6~
Fig. 15 is a perspective view showing a second
embodiment of the invention.
Fig. 16 to 24 are perspective views showing the
sequential steps for the manufacture thereof, therein Fig.
16 shows the step of forming a series of multi-facet
grooves, Fig. 17 the step of charging oxide glass, Fig. 18
the step of forming a second series of multi-facet grooves,
Fig. l9 the step of forming a non-magnetic film having high-
hardness, Fig. 20 the step of forming a ferromagnetic metal
thin film, Fig. 21 the step of forming the non-magnetic film
having high-hardness, Fig. 22 shows the step of charging
molten oxide glass and the surface grinding step, Fig. 23
the step of forming the winding slot, and Fig. 24 the step
of melt bonding or glass bonding.
Fig. 25 to 33 are perspective views showing the process
steps for a third embodiment of the present invention,
wherein Fig. 25 shows the step of forming a first series of
grooves, Fig. 26 the step o~ charging the glass with high
melting temperature, Fig. 27 the step of forming a second
series of grooves, Fig. 28 the step of forming a non-magnetic
film having high-hardness, Fig. 29 the step of forming the
ferromagnetic metal thin film, Fig. 30 the step of forming a
non-magnetic film having high-hardness, Fig. 31 the step of
charging molten oxide glass filler and the surface grinding
step, Fig. 32 the step of forming the winding slot and
~%3~
Fig. 33 the step of melt bonding or glass bonding.
Fig. 34 is a perspective view showing the magnetic
transducer head manufactures by the process steps of
Fig. 25 to 33.
Figs. 35 to 37, are perspective views showing
three further embodiments of the present invention.
Fig. 38 is a perspective view showing the
arrangement of the conventional magnetic transduer
head.
Description of the Preferred Embodiments
To overcome the drawbacks existing in the prior
art, we proposed a novel composite type magnetic
transducer head suitable for high density recording
on high coercive force magnetic tape, such as metal
magnetic tape disclosed in our copending U.S. Patent
application Serial No. 686540 filed Dec. 26, 1984.
The magnetic transducer head is composed of a pair
of magnetic core elements 101, 102 of ferromagnetic
oxides such as Mn-Zn ferrite, as shown in Fig. 38.
The abutment sides of these core elements are cut
obliquely for defining surface 103, 104. On these,
the ferromagnetic metal thin films 105, 106, such
as Fe-Al-Si alloy (so-called Sendust) are deposited
by employing the physical vapor deposition. The
magnetic gap 107 is defined by abutting the
~2;~L626
ferromagnetic metal thin films 105, 106 to each other,
and glass fillers 108, 109 having low melting point or
glass fillers 110, 111 having high melting point are
charged in the molten state for procuring the contact
surface with the tape and preventing the wear of the
ferromagnetic metal thin films 105, 106. The magnetic
transducer head is superi.or in operational reliability,
magnetic properties and wear resistance.
However, these composite type magnetic transducer
heads suffer from inconveniences especially as to the
behavior of the boundary layers between the different
kinds of materials, such as the ferromagnetic oxide -
ferromagnetic metal thin film - oxide glass boundary
layers.
For example, when the ferromagnetic metal thin
film is deposited as by sputtering on the ferromagnetic
oxide (ferrite), the ferrite interface in contact with
the metal is subjected to an elevated temperature in
the range of 300 to 700C. This causes the reaction
to take place on the ferromagnetic metal thin film -
ferromagnetic oxide interface and the oxygen atoms in
the ferrite start to be diffused towards an equilibrium
state in the temperature range of 300 to 500C so as
to be bonded with Al, Si and Fe. The result is that
the ferrite surface is slightly deoxidized and the
~Z3~6;~
contents of oxygen atoms are decreased so that the
boundary layer with inferiority in the magnetic proper-
ties is produced on the interface between the ferrite
and the ferromagnetic metal thin film. When the
boundary layer with the inferrior magnetic properties
is produced in this manner, the soft magnetic proper-
ties of the ferrite are lowered by increase in the
magnetic reluctance in the layer, so that the recording
characteristics and reproduction output of the magnetic
transducer head is lowered. In addition, the magnetic
transducer head is formed by the ferromagnetic metal
thin films and the ferromagnetic oxides having different
thermal expansion coefficients. For example, the thermal
expansion coefficient for Fe-Al-Si alloy is 130 to
160 x lO-~/C., whereas that of the ferrite is 90 to
llO x lO 7/oC. Thus a stress is necessarily induced in
the material in the course of the post-sputtering process
such as melt bonding process, resulting in the destruction
or breakage of the ferromagnetic metal thin films or
deterioration in mechanical properties.
Also, when the glass is directly charged in the
molten state after the deposition of the Fe-Al-Si alloy,
the ferromagnetic metal material may be eroded by some
kinds of molten glass. The reaction between the metal
and the glass may cause the edge or surface of the
~234~
ferromagnetic metal thin films to be deformed thus affect-
ing the material properties or dimensional accuracy.
With some kinds of the materials directly contacting with
molten glass, problems are presented such as decreased
fluidity or bubbles in the molten glass.
The magnetic transducer head according to a first
embodiment of the present invention is firstly explained,
in which a ferromagnetic metal thin film is continuously
formed from the front side or the contact surface of the
head with the magnetic tape to the back side or the bac~
gap forming surface of the magnetic transducer head.
Fig. 1 is a perspective view showing an example of
the composite magnetic transducer head embodying the
present invention. Fig. 2 is a plan view showing the
contact surface of the head with the magnetic tape, and
Fig. 3 is a perspective view of the magnetic transducer
head shown exploded along the gap forming surface.
This head is composed of core elements 10, 11 formed
of ferromagnetic oxides, such as ~In-Zn ferrite. On the
junction surfaces of the core elements 10, 11, there are
formed ferromagnetic metal thin films 13 of ferromagnetic
metal or high permeability metal alloy, such as Fe-Al-Si
alloys, by using the physical vapor deposition method, such
as sputtering by the medium of non-magnetic films having
high-hardness 12. The film 13 are continuously formed from
-- 10 --
12~6;2 ~
the front gap forming surface to the rear gap forming sur-
face. These core elements 10, 11 are placed in abutment
with each other with the intermediary of a spacer formed of
e.g. SiO2 so that the abutment surfaces of the thin films
13 are used as a magnetic gap g with a track width Tw.
When seen from the contact surface with the magnetic tape,
the thin films 13 are deposited on the core elements 10,
11 along a straight continuous line inclined an angle
with respect to a magnetic gap forming surface 14 or the
junction or abutment surfaces of the magnetic core elements
10, 11.
Non-magnetic films having high-hardness 15 are also
formed on the ferromagnetic metal thin films 13. In the
vicinity of the magnetic gap surface or on both sides of a
magnetic gap g on the head surface facing to the magnetic
tape is filled non-magnetic oxide glass at 16, 17 for
defining the track width.
The angle between the ferromagnetic metal thin film
forming surfaces lOa, lla and the magnetic gap forming sur-
face 14 is preferably in the range from 20 to 80. The
angle ~ less than 20 is not preferred because of increased
crosstalk with the adjoining tracks. Thus, the angle larger
than 30 is most preferred. The angle e less than about 80
is also preferred because wear resistance is lowered with
the angle equal to 90. The angle ~ equal to 90 is also
-- 11 --
~l23~6~
not preferred because the thickness of the thin film 13
need to be equal to the track width Tw which gives rise
to the nonuniform film structure and the time-consuming
operation in forming the thin film in vacuum or under
reduced pressure.
The deposited metal thin film 13 need only be of a
film thickness t such that
t = Tw sin ~
wherein Tw represents a track width and ~ represents an
angle between the surfaces lOa, lla and the magnetic gap
forming surface 14. The result is that the film need not
be deposited to a thickness equal to the track width and
hence the time required for the preparation of the magnetic
transducer head may be notably reduced.
The metal thin films 13 may be formed of the ferro-
magnetic metals including Fe-Al-Si alloys, Fe-Al alloys,
Fe-Si alloys, Fe-Si-Co alloys, Ni-Fe alloys (so-called
permallovs), ferromagretic amorphous metal alloys, such as
metal-metalloid amorphous alloys, e.g. an alloy of one or
more elements selected from the group of Fe, Ni and Co
with one or more elements selected from the group of P, C,
B and Si, or an alloy consisting essentially of the firstly
mentioned alloy and containing Al, Ge, Be, Sn, In, Mo, W,
Ti, Mn, Cr, Zr, Hf, or Nb, or a metal-metal amorphous alloy
consisting essentially of transition metal elements and
- 12 -
~3~6~6
glass forming metal elements such as Hf or Zr.
The films 13 may be deposited by any of the vacuum
film forming me.hods including flash deposition, vacuum
deposition, ion plating, sputtering or cluster ion beam
methods.
Preferably, the composition of the Fe-Al-Si alloys
is so selected the Al contents are in the range from 2 to
10 weight percent, and the Si contents are in the range
from 4 to 15 weight percent, the balance being Fe. Thus
it is preferred that, when the Fe-Al-Si alloys are
expressed as
Fe a Al b Si c
where, a, b, and c represent the weight ratio of the
respective associated components, the values of a, b and
c are in the range such that
70 _ a ~ 95
2 _ b _ 10
4 ' c _ 15
If the Al or Si contents are too low or too high,
magnetic properties of the Fe-Al-Si alloys are lowerd.
In the above composition, a part of Fe may be
replaced by at least one of Co and Ni.
The saturation magnetic flux density may be improved
by replacing a part of Fe with Co. Above all, the maximum
saturation magnetic flux density Bs may be achieved when
~Z3~L62~i
40 weight percent of Fe is replaced by Co. Preferably,
the amount of Co is 0 to 60 weight percent relative to
Fe.
On the other hand, by replacing a part of Fe with
Ni, magnetic permeability may be maintained at a higher
value without lowering the saturation magnetic flux densi-
ty Bs. In this case, the amount of Ni is preferably in
the range from 0 to 40 weight percent related to Fe.
Other elements may also be added to the Fe-Al-Si
alloys for improving its corrosion and wear resistance.
The elements that may be used as such additives may include
IIIa group elements including lanthanides such as Sc, Y,
La, Ce, Nd and Gd; IVa group elemen-ts such as Ti, Zr or Hf;
Va groups such as V, Nb or Ta; VIa group elements such as
Cr, Mo or W; VIIa group elements such as Mn, Te or Re; Ib
group elements such as Cu, Ag or Au; elements of the plati-
num group such as Ru, Rh or Pd; and Ga, In, Ge, Sn, Sb or
Bi.
When employing the Fe-Al-Si alloy, the ferromagnetic
metal thin films 13 are preferably deposited in such a
manner tha-t the direction of the columnar crystal growths
be inclined at a predetermined angle ~ of 5 to 45 with
respect to a normal line drawn to the surfaces 10a, lla of
the magnetic core elements 10, 11.
When the thin films 13 are caused to grow in this
:~ 23~6;~:~
manner a-t a predetermined angle ~ with respect to the
normal line drawn to the surfaces lOa, lla, the magnetic
properties of the resulting ferromagnetic metal thin films
13 are stable and superior resulting in improved magnetic
properties of the magnetic transducer head.
Although the films 13 are formed as the single layer
by the above described physical vapor deposition, a plural-
ity of thin metal layers may be also be formed with an
electrically insulating film or films such as SiO2, Ta205,
A1203, ZrO2 or Si3N4 between the adjacent thin metal layer
or layers. Any desired number of the ferromagnetic metal
layers may be used for the formation of the metal thin film.
The non-magnetic films having high-hardness 12 inter-
posed between the core elements 10, ll and the metal thin
films 13 may be formed of (A) one or more of oxides such
s Si2~ Ti2~ Ta25~ A12O3, Cr203 or the glass with high
melting temperature, and deposited to a film thickness of
50 to 2000 A, or formed of (B) non-magnetic metals such as
Cr, Ti or Si either singly or as an alloy and deposited to
a film thickness of 50 to 2000 A. The materials of the
groups (A) and (B) may be used separately or concurrently.
An upper limit is set to the non-magnetic films having high-
hardness 12 because of the pseudo-gap and since the magnetic
reluctance is no longer negligible for a higher film thick-
ness.
~;~3~ 6
By forming the non--magnetic film having high-hardness
15 on -the metal thin film 13, the high-output magnetic trans-
ducer head may be obtalned by reason of the decreased glass
erosion, decreased breakage of the ferromagnetic metal thin
film 13, im roved dimensional accuracy, glass fluidity or
yield rate, and dispersion of the residual strain induced
by glass bonding. The non-magnetic film having high-
hardness 15 may be formed of refractory metals such as W,
Mo or Ta and oxides thereof, in addition to the materials
of the groups (A) and (B) for the non-magnetic films having
high-hardness 12. These materials may be used singly or
as an admixture, such as Cr, Cr ~ Ta205 + Cr, Cr ~ SiO2 ~ Cr,
Ti + TiO2 ~ Ti, and are formed to a thickness less than
several microns.
- Thus, as shown for exàmple in Fig. 4, a non-magnetic
film having high-hardness 12 of the dual layer structure
consisting of a SiO2 layer 12a and a Cr layer 12b is pro-
vided between the core elements 10, 11 and the metal thin
film 13, and a non-magnetic film having high-hardness 15
of a triple layer structure consisting of a Cr layer 15a,
Ta20s layer 15b and a second Cr layer 15c may be formed
between the metal thin film 13 and the oxide glass 16.
In the above described magnetic transducer haed, the
ferromagnetic metal -thin films 13 are deposited on the
surfaces lOa, lla of the ferrite core elements 10, 11
- 16 -
~2346~6
through the intermediary of the non-magnetic films having
high-hardness 12. This prevents the diffusion into the
metal thin films 13 of the oxygen atoms of the ferrite on
account of the presence of the non-magnetic films having
high-hardness 12 even under high temperature conditions
prevailing during the sputtering, for preventing the forma-
tion of the boundary layer with inferiority in the magnetic
properties. Hence, the soft magnetic properties of the
vicinity of the surfaces lOa, lla connected by a magnetic
circuit to the metal thin film 13 are not deteriorated so
that the reduction in the recording characteristics and
playback output of the magnetic head is prevented from
occurring. Also, since the surfaces lOa, lla on which are
formed the magnetic metal thin films 13 are inclined at a
certain angle with respect to the magnetlc gap forming
surface 14, pseudo gaps are not induced even when the non-
magnetic films having high-hardness 12 are of a certain film
thickness. The film 12 with too large a thickness is however
not desirable for the proper function of the magnetic circuit.
Upon comparative tests on the playback output of the
magnetic transducer head with that of the conventional
magnetic head have revealed that an increase in the output
level of the order of 1 to 3 dB may be obtained with the
signal frequency e.g. of 1 to 7 MHz.
Since the aforementioned boundary layer is not formed
- 17 -
~L~23~626
during the sputtering step, limitations on the sputtering
speed or temperature may be removed partially resulting in
the facilitated manuEacture of the transducer head.
Also, since the thermal stress induced by the
differential thermal expansion between the ferrite core
elements 10, 11 and the ferromagnetic metal thin films
13 is relaxed by the presence of the non-magnetic films
having high-hardness 12, no cracks are formed in the
metal thin film 13 even upon cooling following the
sputtering or upon heating caused by subsequent step of
glass melting. This is also favorable in improving the
magnetic properties.
Likewise, since the non-magnetic film having high-
hardness 15 is formed between the film 13 and the oxide
glass 16, it is possible to inhibit the elongation of the
ferromagnetic metal thin films 13 or to provide only a
so-called short-range strain by dispersing the strain
induced between the core elements 10, 11 and the oxide
glass 16. Cracks or wrinkles in the films 13 are also
prevented for improving the operating reliability of the
magnetic head and the yield rate in the manufacture of
the transducer head.
It should be noted that the non-magnetic films having
high-hardness may be provided on the interface between the
core elements 10, 11 and the metal thin films 13 as shown
- 18 -
~3gL6~
in Fig. 5 or on the interface between the metal thin films
13 and the oxide glass 16 as shown in Fig. 6. In Figs. 5
and 6, the same parts or components as those shown in Fig.
1 are indicated by the same reference numerals.
The manufacture process of the above described em-
bodiment will be explained for clarifying the structure
of the magnetic transducer head.
In preparing the magnetic transducer head of the
present embodiment, a plurality of parallel vee grooves
21 are transversely formed on the upper surface 20a of a
substrate 20 of ferromagnetic oxides, such as Mn-Zn ferrite,
with the aid of a revolving grindstone, for forming a sur-
face 21 on which to deposit the ferromagnetic metal thin
films (Fig. 7). The upper surface 20a represents the junc-
tion or abutment surface of the ferromagnetic oxide substrate
20 with the corresponding surface of a mating substrate.
The surface 21 is formed as an inclined surface having a
present angle of inclination ~ (equal to about 45 in the
present embodiment) with respect to the magnetic gap form-
ing surface of the substrate 20.
Then, as shown in Fig. 8, a non-magnetic film having
high-hardness 22 is formed as by sputtering on the upper
surface 20a of the ferromagnetic oxide substrate 20. This
film 22 is formed by providing a first non-magnetic film
having high-hardness by depositing e.g. SiO2 to a thickness
-- 19 --
~L~3~
of 300 A and a second non-magnetic film having high-hardness
by depositing a Cr film to a thickness of 300 A on the first
non-magnetic film having high-hardness~
Then, as shown in Fig. 9, Fe-Al-Si alloy or amorphous
alloy is applied to the non-magnetic film having high-
hardness 22 by employing any of the physical vapor deposi-
tion such as sputtering, ion-plating or vacuum deposition,
for providing the ferromagnetic metal thin film 23.
Then, as shown in Fig. 10, a non-magnetic film having
high-hardness 24 is also formed on the ferromagnetic metal
thin film 23. The film 2~ is formed by applying a first
Cr film to a thickness of approximately 0.1 um, then apply-
ing a Ta2O5 film to a thickness of 1 ~m and finally apply-
ing a second Cr film to a thickness of approximately 0.1 ~m.
The film 24 is preferably formed of high-melting metal such
as W, Mo, Si or Ta, oxides or allovs therof, and deposited
to a thickness less than several microns. The bonding of
the non-magnetic film having high-hardness 24 to the ferro-
magnetic metal thin film is improved by the first Cr
film.
Then, as shown in Fig. 11, on oxide glass filler 25
such as the glass with the low melting point is filled in
the first grooves 21 in which the films 23, 22, 24 are pre-
viously deposited. The upper surface 20a of the substrate
20 is ground smooth for exposing on the upper surface 20a
- 20 -
~L~23~
the ferromagnetic metal thin film 23 deposited on the
surface 21a.
Then, as shown in Fig. 12, adjacent to the surface
21a on which is previously applied the ferromagnetic metal
thin film 23, a second groove 26 is cut in parallel to the
first groove 21 and so as to slightly overlap with one side
edge 21a of the first groove 21. The upper surface 20a of
the substrate 20 is then ground to a mirror finish. As a
result of this process step, the track width is regulated
in such a manner that the magnetic gap is delimited solely
by the ferromagnetic metal thin film.
The second groove 26 may also be polygonal in cross-
section instead of being vee shaped and the inner wall
surface of the groove 26 may be stepped with two or more
stages for procuring a distance from the ferromagnetic
oxide and the ferromagnetic metal thin films when viewed
from the contact surface with the tape. With the groove
configuration, it is possible to reduce the crosstalk
otherwise caused by the reproduction of the long wave-
length signals may be reduced while the large junction
area between the ferromagnetic oxide and the ferromagnetic
metal thin film is ensured. Also, with the above groove
configuration, the end face of the ferromagnetic oxide
is inclined in a direction different from the azimuth
angle direction of the magnetic gap so that signal pickup
- 21 -
~L23~L6~
from the adjoining or next adjoining track or crosstalk may
be reduced by virtue of the azimuth loss.
Also, since the ferromagnetic metal thin film 23 is
first formed on the surface 21a and the second groove 26
is then formed for the regulation of the track width, it
is possible to manufacture the magnetic transducer head
with high yield rate and high accuracy of the track width
by adjusting the machining position of the second groove
26. Thus, when the transducer head is of the type in which
the magnetic flux is passed through the ferromagnetic oxide
via a minimum distance from the magnetic gap formed only by
the ferromagnetif metal thin film, the output and produc-
tivity as well as operating reliability of the head are
improved with low manufacture costs.
A pair of similar ferromagnetic oxide substrates 20
are formed by the above described process. A groove is cut
on one of the substrates at right angle with the first groove
21 and the second groove 26 for providing a ferromagnetic
oxide substrate 30 provided with a winding slot 27 (Fig. 13).
A gap spacer is then applied on the upper surface 20a
of the substrate andtor the upper surface 30a of the sub-
strate 30. Then, as shown in Fig. 14, these substrates 20,
30 are positioned with the respective metal thin films 23
abutting to each other. These substrates 20, 30 are bonded
with molten glass while simultaneously the second groove 26
~ 3~ 3
is charged with molten glass 28. The gap spacer may be
formed of SiO~, ZrO2, Ta2Os or Cr, as desired. In the
above process, charging of the glass 28 in the second
groove 26 need not be effected simultaneously with the
bonding of the substrates 20, 30. Thus the glass 28 may
be charged in the step shown e.g. in Fig. 13 so that the
step shown in Fig. 14 may consist only of the glass bond~
ing step.
The superimposed substrates 20, 30 may then be sliced
along e.g. lines A-A and A'-A' in Fig. 14 for producing
a plurality of head chips, and the contact surface of
each heacl chip with the magnetic tape is then ground to a
cylindrical surface for providing the magnetic transducer
head shown in Fig. 1. The slicing direction through the
substrates 20, 30 may be inclined with respect to the
abutment surface for providing the azimuth recording mag-
netic transducer head.
It should be noted that one of the core elements 10
consists essentially of the ferromagnetic oxide substrate
20 while the other co~e element 11 consists essentially of
the ferromagnetic oxide substrate 30. The ferromagnetic
metal thin film 13 corresponds to the ferromagnetic metal
thin film 23 and the non-magnetic films having high-hardness
12, 15 correspond to the non-magnetic films having high-
hardness 22, 24, respectively. The ferromagnetic metal
- 23 -
~L~3~
thin film 23 formed on a planar surface exhibits high uni-
form magnetic permeability along the path of magnetic flux.
The magnetic transducer head according to a modified
embodiment in which the ferromagnetic metal thin film is
rormed only in the vicinity of the magnetic gap is here-
after explained by referring to Fig. 15.
In the present embodiment, the ferromagnetic metal
thin film is formed only in the vicinity of the magnetic
gap of the magnetic transducer head, wherein a pair of
magnetic core elements 40, 41 are formed of ferromagnetic
oxides such as Mn-Zn ferrite and the ferromagnetic metal
thin films 42 are formed only on the front depth side in
the vicinity of the magnetic gap g by applying the high
permeability alloy such as Fe-Al-Si alloy thereto by the
physical vapor deposition such as sputtering. Oxide glass
fillers 43, 44 are charged in the molten state in the vi-
cinity of the gap forming surface. The non-magnetic films
having high-hardness 45 consisting, for example, of oxides
such as SiO2, TiO2 or Ta205 or non-magnetic metals such as
Cr, Ti or Si are provided between the ferromagnetic metal
thin films 42 and the magnetic core elements 40, 41 of
ferromagnetic oxides, as in -the preceding embodiment.
Non-magnetic films having high-hardness 46 consisting, for
example, of refractory metals or oxides thereof, such as
Ta25, Cr, TiO2 or SiO2, are provided between the metal thin
- 24 -
~L~3~6~6
films 42 and the oxide glass fillers 43. The metal thin
films 42 are inclined at a preset angle ~ relative to the
magnetic gap forminy surface when seen from the contact
surface with the tape, as in the preceding embodiment.
The magnetic transducer head may be manufactured by
the manufacture process steps shown in Figs. 16 to 24.
Firstly, as shown in Fig. 16, a plurality of grooves
Sl of polygonal cross-section are formed on one longitudi-
nal edge of the ferromagnetic oxide substrate SO of Mn-Zn
ferrite by means of a rotary grindstone or with the aid of
electrolytic etching. The upper surface 50a of the substrate
50 corresponds to the magnetic gap forming surface and
the multi-facet groove Sl is provided in the vicinity of
the magnetic gap forming position of the substrate SO.
Then, as shown in Fig. 17, oxide glass fillers S2 are
filled in the molten state in the groove Sl, and both the
upper surface 50a and the front surface SOb are ground
smooth.
Then, as shown in Fig. 18, a plurality of vee grooves
S3 are formed on the substrate edge so as to be adjacent
to and partly overlap with the one facet of the groove 51
in which the glass filler is previously filled as described
hereinabove. At this time, part of the glass 52 is exposed
on the facet or inner wall surface S3a of the groove 53.
The line of intersection S4 between the inner wall surface
53a and the upper surface 50a is normal to the front surface
50b of the substrate 50. The angle the inner wall surface
53a makes with the upper surface may for example be 45.
Then, as shown in Fig 19, SiO2 is applied to a thickness
of, for example, 300 A so as to cover at least the grooves
53 of the substrate 50. Then, Cr is applied to a thickness
of 300 A for providing a non-magnetic film having high-
hardness 55.
Then, as shown in Fig. 20, a high permeability alloy
such as Fe-Al-Si alloy is formed in the vicinity of the
grooves 53 over the non-magnetic film having high-hardness
55 by any of the above described physical vapor deposition
such as sputtering, for providing the ferromagnetic metal
thin film 56. During formation of the metal thin film 56,
the substrate 50 may be disposed with a tilt in the
sputtering apparatus so that the ferromagnetic metal may be
efficiently deposited on the facet or inner wall surface
53a of the groove 53.
On the thus deposited metal thin film 56, the non-
magnetic film having high-hardness 57 formed of, for example,
Ta2Os, TiO2 or SiO2 is deposited as by sputtering (Fig. 21).
In the present example, the dual non-magnetic film having
high-hardness 57 is formed by applying a Cr film on the
metal thin Eilm 56 to a thickness of 0.1 ~m by sputtering
and applying a Ta2Os film thereon to a thickness of
- 26 -
~2~6~
approximately 1 ~m, also by sputtering. By thus forming the
Cr film on the metal thin film 56, the state of deposition
of the Ta2Os film on the metal thin film is improved.
Although the non-magnetic film having high-hardness 57 of
the present embodiment consists of the Cr and Ta2Os layers,
it may also be formed by depositing the Cr-SiO2-Ta2Os lay-
ers in this order or by depositing the Ti iilm to about 1
~m and the TiO2 layer to about 1 ~m in this order.
Then, in the groove 58 in which the non-magnetic film
having high-hardness 55, the ferromagnetic metal thin film
or layer 56 and the non-magnetic film having high-hardness
57 are deposited one upon the other, the oxide glass 58
lower melting than the oxide glass 52 is filled in the
molten state (Fig. 22). The upper surface 50a and the
front surface 50b of the substrate 50 are ground to a
mirror finish. On the front surface 50b of the substrate
50, the ferromagnetic metal thin film 56 formed on the
inner wall surface 53a of the groove 53 is sandwitched
between the previously applied non-magnetic films having
high-hardness 55, 57.
For forming the winding slot side magnetic core ele-
ment, a winding slot 59 is cut in the ferromagnetic oxide
substrate 50 previously processed as described above (Fig.
22) for providing the ferromagnetic oxide substrate 70
shown in Fig. 23.
~LZ3~6~2~
The substrates 50, 60 are abutted to each other as
shown in Fig. 24, with the upper or magnetic gap forming
surface 50a of the substrate 50 in contact with the upper
or magnetic gap forming surface 60a of the substrate 60 by
the intermediary of a gap spacer affixed to one of the
upper surfaces 50a, 60a, and are bonded together by molten
glass to a composite block which is then sliced along lines
B-B and B'-B' in Fig. 24 for providing a plurality of head
chips. The slicing operation may also be performed with
the block inclined azimuth angle.
The contact surface of the head chip ~ith the
magnetic tape is ground to a cylindrical surface for com-
pleting the magnetic transducer head shown in Fig. 15.
It should be noted that one of the magnetic core ele-
ments 41 of the magnetic transducer head shown in Fig. 15
consists essentially of the ferromagnetic oxide substrate
51, while the other core element 40 consists essentially
of the ferromagnetic oxide substrate 60. The non~magnetic
films having high-hardness ~15, 46 correspond to the non-
magnetic films having high-hardness 55, 57, respectively,
whereas the ferromagnetic metal thin film 42 corresponds
to the ferromagnetic metal thin film 56. The oxide glass
filler 43 corresponds to the oxide glass filler 58.
With the magnetic transducer head constructed as
described hereinabove, the ferromagnetic metal thin film 42
- 28 -
~23~;L6~6
exhibits a high uniform magnetic permeability along the
direction of the path of magnetic flux thus assuring a high
stable output of the magnetic transducer head. Also the
ferromagnetic metal thin film is protected by the non-
magnetic films having high-hardness 45 against cracking or
deformation.
Also, with the magnetic transducer head of the present
embodiment, the ferromagnetic oxides are directly bonded
together by glass on the back junction surface or back gap
surface thus providing large destruction strength of the
head chip and improved yield rate while assuring stabillty
of the ferrQmagnetic metal thin film. Also, since the
metal thin film is formed only in the vicinity of the mag-
netic gap g, the metal thin film 42 need be formed on a
relatively small area. Thus the number of items disposable
in one lot in the sputtering apparatus may be increased
resulting in improved mass producibility.
A further example of the magnetic transducer head
manufactured by an alternative process is explained by
referring to Figs. 25 to 34.
In preparing the magnetic transducer head, as shown
in Fig. 25, a plurality of square shaped grooves 71 are
formed obliquely on the upper surface 70a corresponding to
the contact surface with the magnetic tape of the ferro-
magnetic oxide substrate 70 formed e,g. of Mn-Zn ferrite.
- 29 -
~23~
The grooves 71 are of such a depth as to reach the winding
slot of the head.
Then, as shown in Fig. 26, the glass filler 72 having
the high melting temperature is filled in the molten state
in the grooves 71. The upper surface 70a and the front
surface 70b are then ground smooth.
Then, as shown in Fig. 27, a plurality of second
square shaped grooves 73 are formed on the upper surface
70a in the reverse oblique direction to and for partially
overlapping with the first square shaped grooves 71 filled
previously with the glass filler 72. The aroove 73 is of
nearly the same depth as the groove 71. ~The inner side 73a
of the groove 73 is normal to the upper surface 70a of the
substrate 70 and makes an angle of e.g. 45 with the front
surface 70b. The inner side 73a of the groove 73 intersects
the associated first groove 71 in the vicinity of the front
side 70b of the substrate 70 for slightly cutting off the
glass filler 72.
After the grooves 71, 73 are formed in this manner on
the upper surface 70a of the ferromagnetic oxide substrate
70, a non-magnetic film having high-hardness 74 of e.g. SiO2
or Cr is deposited in the vicinity of the groove 73 of the
substrate 70, as shown in Fig. 28, by employing any of the
above described physical vapor deposition, such as sputter-
ing. The non-magnetic film having high-hardness 74 may be
- 30 -
~3g~6
formed of the same materials as explained in the preceding
embodiments.
Then, as shown in Fig. 29, a high permeability alloy
layer, such as Fe-Al-Si alloy layer is formed on the film
74 for providing a ferromagnetic metal thin film 75 by
employing any of the above described physical vapor deposi-
tion, such as sputtering. The substrate 70 may be disposed
with a tilt in the sputtering apparatus for achieving an
efficient deposition of the alloy layer.
Then, as shown in Fig. 30, high-hardness metals,
oxides or alloys thereof are applied to the film 75 as by
sputtering, for providing the non-magnetic film having high-
hardness 76. The non-magnetic film having high-hardness 76
may be formed of the same materials as explained in the
preceding embodiments in one or plural layers.
Then, as shown in Fig. 31, in the grooves 73 in which
the non-magnetic films having high-hardness films 74, 76
and the ferromagnetic metal thin film 75 are deposited one
upon the other, an oxide glass filler 77 lower melting than
the glass filler 72 charged in the groove 71 is charged
in the molten state. The upper surface 70a and the front
surface 70b of the substrate 70 are ground to a smooth
mirror finish. The result is that the metal thin film 75
is sandwitched and protected by the non-magnetic films
having high-hardness 74, 76 on the inner side 73a of the
~2;:~6~6
groove 73. Although the films 74, 75, 76 persist on the
other inner side and bottom of the groove 73, they are in
negligible amounts and hence are not shown in the drawing.
Then, a winding slot 78 is cut on one of the sub-
strates for providing the ferromagnetic oxide substrate
80 (Fig. 32).
Then, as shown in Fig. 33, the substrate 80 provided
with the winding slot 80 and the substrate 70 not provided
with the winding slot are placed side by side with the
intermediary of a gap spacer deposited on at least one of
the magnetic gap forming front surface 70b, 80b, so that
the metal thin films abut each other. The substrates 70,
80 are then united together by glass or melt bonding to a
unitary block.
The block thus formed by the substrates 70, 80 are
sliced along lines C-C and C'-C' in Fig. 33 for forming
plural head chips. The abutting surfaces of these head
chips with the magnetic tape are then ground to a cylindri-
cal surface for completing the magnetic transducer head
shown in Fig. 34.
With the magnetic transducer head shown in Fig. 34,
one of the magnetic core elements 81 corresponds to the
ferromagnetic oxide substrate 70, while the remaining core
element corresponds -to the ferromagnetic oxide substrate
80. The ferromagnetic metal thin film 84 corresponds to
~3~6~
the ferromagnetic metal thin film 75, whereas the non~
magnetic films having high-hardness 83, 85 correspond to
the non-magnetic films having high-hardness 74, 76,
respectively. The oxide glass filler 86 corresponds to
the oxide glass filler 77.
In ~he magnetic transducer head shown in Fig. 34,
the ferromagnetic metal thin film 84 is sandwitched and
protected by the non-magnetic films having high-hardness
83, 85 against cracking, deformation or deterioration in
the boundary surface with the ferromagnetic oxides, simi-
larly to the preceding embodiments, so that optimum results
are achieved as in the case of the magnetic transducer heads
shown in Figs. 1 and 15. The metal thin film 84 is inclined
at a preset angle to the surface forming the magnetic gap g
and is formed linearly and continuously on one and the same
surface thus assuring a high uniform magnetic permeability
along the path of magnetic flux and providing a high stable
output, as in the preceding embodiments.
The present invention is also applied to a magnetic
transducer head in which the vicinity of the contact
surface with ihe magnetic tape is protected by the non-
magnetic elements having high-hardness, such as ceramic
elements.
Figs. 35 to 37 show an embodiment of the magnetic
transducer head in which the vicinity of the contact
~23~6~
surface with the magnetic tape is protected by non-
maqnetic elements having high-hardness, such as ceramic
elements.
The magnetic transducer head shown in Fig. 35
corresponds to that shown in Fig. 1 so that components
same as those shown in Fig. 1 are indicated by the same
reference numerals. Thus the magnetic transducer head
shown in Fig. 35 corresponds to the head of Fig. 1 where-
in the protective elements 91, 92 formed of non-magnetic
wear-resistant materials such as calcium titanate (Ti-Ca
ceramics), oxide glass chips, titania (TiO2) or alumina
(A1203) are provided in the vicinity of the contact
surface with the magnetic tape. The transducer head of
Fig. 35 consists essentially of a composite substrate
formed by thermal pressure bonding of a highly wear-
resistant non-magnetic substrate of e.g. calcium titanate,
oxide glass, titania or alumina to one end face of a
ferro-magnetic oxide substrate of e.g. Mn-Zn ferrite with
the intermediary of a molten glass plate about several
tens of microns thick. The substrate is processed in
accordance with the process similar to that shown in Figs.
7 to 14. Since the magnetic material such as ferrite is
not exposed on the contact surface with the magnetic
tape, the machining step shown in Fig. 12 for forming the
second groove 26 may be dispensed with.
- 34 -
-
~3~6~6
The magnetic transducer head shown in Fig. 36 corres-
ponds to the magnetic transducer head shown in Fig. 15 and
the components same as those shown in Fig. 15 are indicated
by the same reference numerals. The magnetic transducer
head shown in Fig. 36 corresponds to the magnetic transducer
head shown in Fig. 15 in which protective elements 93, 94
of highly wear-resistant non-magnetic material are provided
to the vicinity of the contact surface with the magnetic
tape. The magnetic transducèr head shown in Fig. 36
is fabricated from the similar composite substrate and by
the manufacture process shown in Figs. 16 to 24. In this
case, the machining step for the groove 51 shown in Fig.
16 and the charging step of the molten oxide glass filler
52 shown in Fig. 17 may be dispensed with.
The magnetic transducer head shown in Fig. 37 corre-
sponds to the magnetic transducer head shown in Fig. 34
and the components same as those of the magnetic transducer
head shown in Fig. 34 are indicated by the same reference
numerals. The transducer head shown in Fig. 37 corresponds
to the head shown in Fig. 34 in which protective elements
95, 96 of highly wear-resistant non-magnetic material are
provided in the vicinity of the contact surface with the
magnetic tape. The magnetic transducer head of the present
embodiment is fabricated from the composite substrates
of the preceding embodiments and by using the process
L6~6
similar to that shown in Figs. 25 to 33. In this case,
the machining step of forming the groove 71 as shown in
Fig. 25 and the charging step of the high melting glass
filler 72 in the molten state as shown in Fig. 26 are
similarly dispensed with.
In the respective magnetic transducer heads shown
in Figs. 35 to 37, wear-resistant non-magnetic elements
are previously bonded to the ferromagnetic oxide block
and ground for forming the abutting surface with the mag-
netic tape. In this manner, the portion of the abutting
surface, inclusive of the gap surface, other than the
magnetic metal thin film, is constructed of the non-magnetic
materials, that is, the wear-resistant non-magnetic material
and the non-magnetic films having high-hardness, so that
the ferromagnetic oxide material is not exposed to the out-
side. Thus the track width is-determined by the size of
the inclined section of the ferromagnetic metal thin film
irrespective of the terminal point of the gap surface
grinding operation following the formation of the ferro-
magnetic metal thin film, thus allowing for broader manu-
facture tolerance of the substrate block. Also the ferro-
magnetic metal thin film is protected by the non-magnetic
film having high-hardness, so that the magnetic transducer
head is protected from deformation, cracking or degradation
on the boundary layer in the course of glass bonding, thus
- 36 -
~:3~
assuring a high yield rate and a high stable output of the
magnetic transducer head. In VTR heads, it is necessary
to make use of single crystal ferrite projecting on the
tape abutment surface because of the increased relative
speed between the head and the tape, resulting in increased
material costs. In the above described embodiments, the
back gap side ferrite is not likely to undergo partial wear
upon contact with the tape so that high-~ polycrystal ferrite
(i.e. sintered type polycrystal ferrite) may be safely used
with an attendant reduction in the material costs.
It will be apparent from the foregoing that the pre-
sent invention provides an arrangement of the magnetic
transducer head according to which non-magnetic film having
high-hardness are interposed between the ferromagnetic
metal thin film and the ferromagnetic oxides so that the
diffusion of the oxygen atoms in the ferromagnetic oxides
is prevented even under the elevated temperature during
the time of application of the ferromagnetic metal thin
film and hence there is no risk that the boundary layer
with inferiority in magnetic properties due to low oxygen
atom contents in not formed in the boundary layer with
the ferromagnetic oxides. The result is that the soft
magnetic properties of the ferromagnetic oxides are not
deteriorated and the recording characteristics and playback
output of the magnetic transducer head is also not lowered.
~1~3~6~6
Since the boundary layer with inferior magnetic prop-
erties is not induced by sputtering, limitations on the
sputtering speed or temperature in the course of applica-
tion of the ferromagnetic metal thin film can be removed
partially with a resulting merit in manufacture efficiency.
The non-magnetic film having high-hardness interposed
between the oxide glass filler and the ferromagnetic metal
thin film is effective to protect the oxide glass and
improve glass fluidity while inhibiting the erosion by
the oxide glass or the deformation of the ferromagnetic
metal thin film.
The provision of the respective non-magnetic films
havlng high-hardness is also effective to improve the
bonding of the ferromagnetic metal thin film and to par-
tially remove local stress such as thermal stress otherwise
caused by the differential thermal expansion between the
adjoinina components during the ost-sputtering process
such ~s cooling process for preventing crack or the like
defects.
Therefore the ferromagnetic metal thin film is more
stable and the magnetic properties are also stable with an
improved accuracy in the track width so that the magnetic
transducer head is reliable in strength and mav be con-
veniently used with a high coercive force magnetic
recording medium.
- 38 -
