JP2547408B2 - Strip magnetic thin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a strip-shaped magnetic thin film, for example, a substantially strip-shaped magnetic thin film used as a yoke for guiding a signal magnetic field to a magnetoresistive effect element or as an induction type magnetic core. It is a thing.

[Prior Art] FIGS. 5 (A) and 5 (B) explain a conventional structure of a magnetoresistive effect type magnetic head (hereinafter referred to as an MR head) as a thin film magnetic head using a band-shaped magnetic thin film of this kind. is there.

As shown in the figure, the MR head includes a magnetoresistive effect element (hereinafter referred to as an MR element) 2 on a non-magnetic substrate 5 that supports the entire MR head, a lead yoke 1 and a tail yoke for guiding and applying an external signal magnetic field thereto. 3 and two electrodes 4 for extracting a signal from the MR element 2 are provided. The upper end surface of the MR head in the figure is formed as a sliding surface 6 that slides on a magnetic recording medium (not shown). The MR element 2, the lead yoke 1 and the tail yoke 3 are made of a strip-shaped magnetic thin film. The yokes 1 and 3 are provided over the MR element 2 via an insulating layer (not shown). The electrode 4 is made of a thin film of good conductor.

In the manufacturing process of the MR head, first, the MR element 2 is formed and patterned on the non-magnetic substrate 5, then the electrode 4 is formed and patterned, and the yokes 1 and 3 are formed through an insulating layer (not shown). The MR head is formed by patterning and further forming an insulating protective layer (not shown) on the entire surface.

In such an MR head, the signal magnetic field from the magnetic recording medium (not shown) sliding on the sliding surface 6 is guided to and applied to the MR element 2 via the yokes 1 and 3 which are strip-shaped magnetic thin films, and the signal magnetic field is applied. The resistance value R of the MR element 2 changes depending on the strength of H,
When the input / output characteristics of the element 2 are good, basically a curve as shown in FIG. 6 is drawn. This curve is called the RH curve. Then, the change in the resistance value R is taken out as an output signal via the electrodes 4, 4.

The yokes 1 and 3 are given uniaxial magnetic anisotropy. The main mode of signal magnetic field transmission in the high-frequency region is magnetization rotation, and the easy axis of magnetization of the yokes 1 and 3 is generally perpendicular to the direction in which the magnetic flux of the signal magnetic field flows.

[Problems to be Solved by the Invention] When detecting a magnetic field with such an MR head, it has been known that the form of magnetic domains generated in the yokes 1 and 3 greatly affects the input / output characteristics of the MR head. Has been.

If an irregular environmental magnetic domain is generated in the yokes 1 and 3, and the magnetic domain shape such as the size and direction of the magnetic domain is disturbed, the head efficiency and the magnetic resistance deteriorate, and the RH curve of the MR element 2 becomes As shown in FIG. 7, it may have a hysteresis or may change irregularly including noise. These hysteresis and noise cause irregularity in the output waveform of the MR head and output fluctuation.

In order to prevent this, conventionally, a strong uniaxial magnetic anisotropy is given to the yokes 1 and 3 by a method such as film formation in a magnetic field or magnetic annealing when forming the thin films of the yokes 1 and 3. A method of clarifying the generation of magnetic domains to suppress disorder is adopted.

The number of magnetic domains is related to the strength of the uniaxial anisotropy of the yokes 1 and 3, that is, the magnitude of the value of the induced magnetic anisotropy magnetic field Hk. It is confirmed that the number of magnetic domains is small, and the number of magnetic domains is large when Hk is large and anisotropy is strong.

When the thin films of the yokes 1 and 3 are formed by normal sputtering, Hk
= 1 to 20e, there is little anisotropy, and the generation of magnetic domains is not clear. However, when a thin film of Hk = 30e is formed by sputtering in a magnetic field, for example, as shown in FIG. Uniaxial anisotropy is given to the thin film 1 ', and three domain walls (hereinafter referred to as 180 ° domain walls) W parallel to the applied magnetic field direction are generated.

However, in the case of sputtering in a magnetic field, unexpected anisotropy is disturbed depending on conditions such as the influence of the magnet in the sputtering apparatus and the incident direction (crystal growth direction) of the magnetic particles forming the thin film on the film formation surface. It may occur. In this case, as shown by the dotted line in FIG. 8, the 180 ° domain wall W does not appear clearly, and the domain wall may even be disturbed.

As described above, the method such as the sputtering in the magnetic field has a problem that the anisotropy control and the magnetic domain generation mode cannot be controlled unless the film formation conditions are extremely limited.

[Means for Solving the Problems] In order to solve such problems, according to the charged magnetic thin film of the present invention, domain walls are generated between each other while facing both side edges along the longitudinal direction. A structure having at least a pair of notches is adopted.

[Operation] According to such a structure, since the domain wall that separates the magnetic domain is generated between the notch pair, the generation mode of the magnetic domain can be controlled by the arrangement of the notch pair. By appropriately arranging the notch pairs, it is possible to clearly generate preferable regular magnetic domains to suppress disturbance of the magnetic domains, prevent adverse effects on the magnetic characteristics due to the disturbance, and obtain good characteristics.

Embodiment An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 uses a strip-shaped magnetic thin film according to an embodiment of the present invention.
The structure of the MR head is shown. In the same figure, the respective parts denoted by the same reference numerals in FIGS. 5 (A) and 5 (B) of the conventional example are common to or correspond to the conventional example, and the description thereof will be omitted.

As shown in FIG. 1, in this embodiment, both side edges of the yokes 1 and 3, which are strip-shaped ferromagnetic thin films, are orthogonal to the sliding surface 6, that is, the vertical direction in the drawing in which the magnetic flux of the signal magnetic field of the yokes 1 and 3 flows. A pair of opposite notches 1a to 3a are formed in this case on each side edge, along with one pair and two pairs.

Specifically, the notches 1a to 3a are formed in a substantially isosceles triangle that is pointed toward the inside of the yokes 1 and 3, and the straight line connecting the apexes of the pair of opposing notches 1a to 3a is the sliding surface 6. They are arranged so as to be parallel, that is, substantially perpendicular to the direction in which the magnetic flux of the signal magnetic field flows.

The yokes 1 and 3 having such cutouts can be formed by ordinary photolithographic etching, in which a master pattern of a magnetic thin film is patterned into a required shape and then etched. Note that the film formation before etching has a Hk of 30 by sputtering in the magnetic field described above.
Form a thin film of about e.

In this way, by providing the cutouts 1a to 3a on the strip-shaped magnetic thin films of the yokes 1 and 3, a magnetic domain wall is generated from the apexes of the cutouts 1a to 3a. Although the causal relationship of this action has not been clarified yet, it has been confirmed by experiments that the domain wall is generated from the notch apex.

Then, a linear 180 ° domain wall is generated between the facing vertices of the notches 1a to 3a, and a magnetic domain is generated by using this as a partition. That is, by arranging the notches 1a to 3a, the size and direction of the magnetic domains generated in the yokes 1 to 3 can be appropriately controlled, and the generation mode of the magnetic domains can be appropriately controlled.

As described above, if the thin films of the yokes 1 and 3 are sputtered in a magnetic field to a film thickness of about Hk = 3 Oe, the 180 ° domain wall W does not appear clearly and is disturbed as shown by the dotted line in FIG. Even there.

Therefore, as shown in FIG. 2, the yoke 1 (or 3)
By forming a triangular notch 1a 'at a position where the 180 ° domain wall W of the thin film 1'corresponding to 1 is formed, the generation of the 180 ° domain wall W can be clarified. Here, the pitch at which the 180 ° domain wall should be generated, that is, the pitch of the magnetic domain is related to Hk of the thin film 1'and the track width b, and is a value obtained by dividing the track width b by Hk. Therefore, the pitch dimension a of the pair of notches 1a 'is set to this value, and for example, when Hk = 3Oe, the track width dimension b is 60 μm.
Then, a is 20 μm. In this way, the generation of the 180 ° domain wall can be clarified as described above, regular magnetic domains can be generated, and disorder of the magnetic domains can be suppressed.

However, as shown in FIG. 2, the notches 1 on both side edges along the direction in which the magnetic flux of the signal magnetic field of the thin film 1 ′ flows.
When the width c of a'is taken corresponding to the pitch a of the pair of notches 1a ', the track width of the thin film 1'of the lead yoke 1 depends on the grinding depth of the sliding surface 6 in the MR head manufacturing process. There is an inconvenience that b changes.

Therefore, as shown in FIG. 3, the width c of the notch 1a of the lead yoke 1 is made smaller than the pitch a of the notch 1a.
The width c is at most 9/10 of the pitch a.

In this way, in the MR head manufacturing process,
When the head before grinding the sliding surface shown in FIG. 4 is ground and polished to the finishing surface 6'of the sliding surface shown by the dotted line, the finishing surface 6'is cut into upper and lower parts as shown in FIG. 3 and FIG. By stopping at the vertical portion between the cutouts 1a, the track width b can be kept constant.

As described above, by providing the cutouts 1a and 3a in the yokes 1 and 3, according to the present embodiment, a domain wall is generated through the cutouts 1a to 3a, and each of the yokes 1 and 3 is ruled equally. Magnetic domains can be stably and clearly generated, and disturbance of magnetic domains due to a reflux magnetic domain can be suppressed. Therefore, it is possible to suppress the occurrence of disturbance such as noise and hysteresis in the RH curve of the MR element 2, and it is possible to obtain good input / output characteristics of the MR head.

In the present embodiment, the yokes 1 and 3 need only have a substantially strip shape, and both side edges may be curved or non-parallel as a whole.

Further, the strip-shaped magnetic thin film of the present invention is not limited to the MR head, but it is clear and stable not only in the induction type magnetic head but also in the thin film magnetic head whose magnetic core is composed of the magnetic thin film, by providing the thin film with the notch as described above. The generation of the magnetic domains stabilizes the input / output characteristics of the head, obtains good characteristics, and improves the magnetic efficiency of the head.

[Effects of the Invention] As is apparent from the above description, according to the strip-shaped magnetic thin film of the present invention, at least a pair of notches that face both side edges along the longitudinal direction and generate domain walls between each other are provided. Since the structure provided is adopted, it is possible to control the generation mode of the magnetic domain through the notch, and it is possible to obtain the excellent effect that the disorder of the magnetic domain is suppressed and the magnetic characteristics are improved and stabilized, and the efficiency is improved. .

[Brief description of drawings]

FIG. 1 shows an MR using a strip-shaped magnetic thin film as an embodiment of the present invention.
FIG. 2 is a plan view showing the structure of the head, FIG. 2 is an explanatory view of a magnetic domain wall generation state in the strip-shaped magnetic thin film of the present embodiment, FIG. 3 is an explanatory view of a yoke thin film having a narrow cutout width, and FIG. FIG. 5A is a plan view of a conventional MR head, and FIG. 5B is a vertical side view of the same. FIG. 6 is a diagram showing a favorable RH curve of the MR element, FIG. 7 is a diagram showing a disordered RH curve, and FIG. 8 is an explanatory diagram of a domain wall generation state in a conventional strip magnetic thin film. . 1 ... Lead yoke, 1a, 3a ... Notch 2 ... MR element, 3 ... Tail yoke 4 ... Electrode, 5 ... Non-magnetic substrate 6 ... Sliding surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideto Sano Hideo Sano 1248 Shimokagemori, Chichibu City, Canon Electronics Co., Ltd. (72) Takeshi Osato 1248 Shimokagemori Shimokage, Chichibu, Canon Inc. (56) ) Reference JP 61-295606 (JP, A) JP 60-55602 (JP, A)

Claims (3)

(57) [Claims] 1. A strip-shaped magnetic thin film which is provided with at least a pair of notches facing both side edges along a longitudinal direction and generating domain walls between them. 2. The notch is formed in a substantially triangular shape that is pointed toward the inside of the thin film, and the straight line connecting the vertices of a pair of opposite notches is arranged so as to be substantially perpendicular to the longitudinal direction. The strip-shaped magnetic thin film according to claim 1, which is characterized. 3. A plurality of pairs of the cutouts are provided at a predetermined pitch,
The strip-shaped magnetic thin film according to claim 2, wherein the width of the cutouts on both side edges along the longitudinal direction of the thin film is smaller than the pitch.