Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1998-04-23
2000-04-18
Kiliman, Leszek
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428692, 428634R, 428634T, 428634TS, 428634TM, 428634TR, 428 30, 2041922, 20419232, 20419237, G11B 566
Patent
active
060513047
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistance element and a manufacturing method therefor. In greater detail, the present invention relates to a magnetoresistance element having a large magnetoresistance (MR) rate of change, as well as to a manufacturing method for this element. The magnetoresistance element of the present invention is optimally applied to heads which reproduce magnetic signals written onto hard disks, floppy disks, magnetic tape, and the like.
2. Description of the Related Art
With respect to conventional magnetoresistance elements and manufacturing methods for such elements, the following technologies have all been reported by Inomata (Kouichiro Inomata: Ouyou Butsuri (applied physics), 63, 1198 (1194)).
FIGS. 5(b) and 6(b) are schematic diagrams showing the cross-sectional structure of conventional magnetoresistance elements. FIG. 5(b) shows an artificial lattice type structure (A) comprising a structure in which, on the surface of a substrate 501, there are a plurality of layers in which a nonmagnetic layer (spacer) 522 is sandwiched between ferromagnetic layers 521. Furthermore, FIG. 6(b) shows a spin valve type (B) having a structure in which, on the surface of a substrate 601, two ferromagnetic layers 621 are laminated with a nonmagnetic layer 622 therebetween, and an antiferromagnetic layer 623 is formed on the surface of the ferromagnetic layer which was provided last.
An example of the (A) artificial lattice type is a structure in which the nonmagnetic layer is formed from a Cr film, and the ferromagnetic layers are formed by Fe; that is to say, a Fe/Cr structure (FIG. 14, M. N. Baibich. et al.: Phys. Rev. Lett. 61, 2472 (1988)). FIG. 14 is a graph showing the change in resistance observed in three types of structures when an external magnetic field was altered. The vertical axis represents a standardization against the value observed in a magnetic field of 0. In the case of Fe/Cr, when the external magnetic field is at 0, the spin of the Fe layers is coupled in a mutually anti-parallel fashion and the resistance is high; it is noted that when a sufficiently large magnetic field (a saturation magnetic field, H.sub.s) is applied, the spin becomes mutually parallel and the resistance drops. The MR ratio at this time (the ratio of the change in resistance with respect to the resistance value in a saturation magnetic field) is 4.2 K and thus roughly 85%; even at room temperature, this is very large, at approximately 20%.
However, there is a problem in that although the Fe/Cr structure has a large MR ratio, H.sub.s is also large, at approximately 1.6.times.1.0.sup.6 A/m (20 kOe).
A structure in which the nonmagnetic layer comprises a Cu film and the ferromagnetic layer comprises a Co film, that is to say, a Co/Cu structure, has also been researched (D. H. Mosca. et al.: J. Magn. & Magn. Mater. 94, L1(1991), and S. S. P. Parkin. et al.: Phys. Rev. Lett. 66, 2152 (1991)). The MR ratio of the Co/Cu structure exceeds 50% at room temperature, and the H.sub.s is also smaller than that of the Fe/Cr.
Research was subsequently conducted on a number of artificial lattices; however, aside from the Fe/Cr system, the systems which have chiefly attracted attention are Co systems and Ni systems in which a noble metal is used as the spacer. Representative examples of these include, for example, Co/Cu, Co--Fe/Cu, Ni--Fe/Cu, Ni--Fe/Ag, and Ni--Fe--Co/Cu. Co systems exhibit a large MR ratio, while Ni systems exhibit a small saturation magnetic field. Fe/Cr systems have a spacer which is a transition metal, and have been studied in comparison with noble metal spacers in order to understand the mechanism thereof.
However, in considering magnetic head uses, it is desirable that H.sub.s be a few hundred Oe, and that a large MR ratio (at room temperature) be present; and there has been a problem in that in each of the systems described above, the confirmed MR ratio is insufficient.
One indication with respect to this problem is the report by the g
Kiliman Leszek
Knuth Randall J.
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