Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1996-12-05
2001-02-13
Davis, David D. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06188550
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for producing thin film magnetic structures and, more particularly, to a method for locally modifying the magnetic characteristics of the thin film magnetic structure.
BACKGROUND AND PRIOR ART
There are prior art techniques for local modification of magnetic material in the fabrication of magnetic devices. Lawrance, U.S. Pat. No. 3,314,056, “Gapless Magnetic Head”, issued Apr. 11, 1967, discloses a magnetic head having a ring core in which the gap is formed by treatment to reduce the permeability in a restricted core region. Neutron bombardment is the preferred method to significantly diminish the magnetic properties in the gap region. The impact of the neutrons serves to strain the existing crystal structure of the localized region so that the magnetic properties of the core material in the treated region are affected.
Boll, U.S. Pat. No. 4,265,684, “Magnetic Core Comprised of Low-retentivity Amorphous Alloy”, issued May 5, 1981, discloses a magnetic head having a ring core made from an amorphous alloy. An effective gap is produced in the core by converting the material in a local region to the crystalline state by localized heating to a temperature above the crystallization temperature of about 400° C.
Otomo et al., U.S. Pat. No. 4,772,976, “Process for Preparing Magnetic Layer and Magnetic Head Prepared Using the Same”, issued Sep. 20, 1988, describe a thin film magnetic head in which ion implantation is used to locally vary the magnetic characteristics of the magnetic material. The ions are then thermally diffused into the material by heat treatment to attain uniform magnetic characteristics.
L. Schultz et al., “Permanent Local Modification of the Magnetic Bubble Properties of Epitaxial Garnet Films By Laser Annealing,” Journal of Applied Physics, Vol. 50, No. 9, September 1979, describe laser annealing of magnetic materials. These studies were aimed toward using a laser to locally increase the magnetization of garnet films for channeling of magnetic bubbles. The changes in magnetic properties that were observed were attributed to a crystallographic site redistribution of the Ga and Fe atoms in annealed regions which support mobile bubbles.
None of the cited references shows a magnetic structure comprising a layer of magnetic material with an overlayer and an underlayer and heat treatment to produce interaction between the materials of the overlayer and the underlayer with the layer of magnetic material to produce selected magnetic and electrical characteristics in localized areas of the layer of magnetic material. However, there is prior art which deals with the local modification of a magnetic structure with an overlayer.
Bajorek et al., U.S. Pat. No. 3,840,898,“Self-biased Magnetoresistive Sensor”, issued Oct. 8, 1974, describe a magnetoresistive sensor in which a protective coating of photoresist is deposited over a preselected portion of an NiFe film, and the structure is then annealed at elevated temperatures in an oxygen-rich atmosphere. The resultant oxidation of the unprotected part of the NiFe film results in depletion of Fe from the bulk of the unprotected part of the film so as to effectively change its composition, and also change its composition-dependent magnetic characteristics.
Bajorek et al., U.S. Pat. No. 3,887,944, “Method for Eliminating Part of Magnetic Crosstalk in Magnetoresistive Sensors”, issued Jun. 3, 1975, disclose an integrated array of side-by-side magnetoresistive (MR) reading heads. To eliminate crosstalk between adjacent MR read heads, a region of high-coercivity material is formed between adjacent MR read heads. The region of high-coercivity material can be produced by exchange coupling through alloying or other chemical reaction, or by chemical treatment, to roughen the MR stripe prior to depositing a conductor into the roughened area.
However, Bajorek et al., in the above two patents, do not teach a purposeful selection of an underlayer as well as an overlayer in producing modification of their magnetic structure. Also, they do not consider the possibility of producing bias fields, the direction of such bias fields, if they do exist, or the subsequent domain states of the MR sensor.
SUMMARY OF THE INVENTION
It is therefore the principal object of this invention to provide a method for producing a magnetic structure in which the electrical and magnetic characteristics of the magnetic structure can be locally modified.
According to the invention, the method comprises the steps of forming a layered structure comprising an underlayer, a layer of magnetic material, and an overlayer, and supplying thermal energy to the magnetic structure in an amount sufficient to provide selective interaction between the materials of the overlayer and the underlayer with the layer of magnetic material to produce predetermined magnetic and electrical characteristics in the layer of magnetic material.
In a specific embodiment, the step of supplying thermal energy is produced by local heating, thereby producing predetermined magnetic and electrical characteristics in selected local areas of the layer of magnetic material.
In another specific embodiment, the step of supplying thermal energy is produced by rapid thermal anneal.
In further specific embodiments, either the underlayer and/or the overlayer are patterned to produce a plurality of separate regions, each having different characteristics.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3314056 (1967-04-01), Lawrance
patent: 3840898 (1974-10-01), Bajorek et al.
patent: 3887944 (1975-06-01), Bajorek et al.
patent: 4265684 (1981-05-01), Boll
patent: 4664941 (1987-05-01), Washburn
patent: 4772976 (1988-09-01), Otomo et al.
patent: 4940511 (1990-07-01), Fontana, Jr. et al.
patent: 5005096 (1991-04-01), Krounbi et al.
patent: 5014147 (1991-05-01), Parkin et al.
patent: 5018037 (1991-05-01), Krounbi et al.
patent: 5100692 (1992-03-01), Nakamura et al.
patent: 5432734 (1995-07-01), Kawano et al.
patent: 5461526 (1995-10-01), Hamakawa et al.
patent: 5461527 (1995-10-01), Akiyama et al.
patent: 5503686 (1996-04-01), Okamura et al.
patent: 7-334818 (1995-12-01), None
R. P. McGouey, “Fabrication of Magnetic Bubble Devices”, IBM Technical Disclosure Bulletin, vol. 21, No. 3, Aug. 1978, pp. 1289-1290.
L. Schultz et al., “Permanent local modification of the magnetic bubble properties of epitaxial garnet films by lasar annelaing” J. Appl. Phys., 50(9), Sep. 1979, pp. 5902-5905.
Fontana, Jr. Robert Edward
Houle Frances Anne
Tsang Ching Hwa
Davis David D.
International Business Machines - Corporation
Saber Paik
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