Anisotropic magnetoresistance and magnetostriction of [Fe15Ni85/Fe25Ni75] and [Co35Ni65/Fe25Ni75] multilayers

摘要

We have made a series of [A(x)B(60-)x](n) multilayers and another series of [CxB60-x](n) multilayers, where A = Fe15Ni85, B = Fe25Ni75, C = Co35Ni65, n = 2 is the period, and x(A) (or x(C)) is the thickness of layer A (or layer C) in nanometer, respectively. The deposition temperature T-s was 340 degreesC. The magnetic properties, such as anisotropic magnetoresistance Deltarho/Deltarho(o), saturation magnetostriction lambda(s), and anisotropy field H-k, were measured. Although Deltarho/Deltarho(o). of the [C-60](2) film is larger than that of the [B-60](2) film, Hk of the former is also much larger. Therefore, the magnetoresistance (MR) sensitivity S, defined as the slope at the point of inflection of the MR curve, is not gained for either single-layered film. A similar situation exists between the [A(60)](2) and [B-60](2) films, except H-k of the former is only slightly larger. Besides, lambda(s) < 0 for Fe15Ni85 alloy (the [A(60)](2) film), lambda(s) < 0 for Co35Ni65 alloy (the [C-60](2) film), and lambda(s) > 0 for Fe25Ni75 alloy (the [B-60](2) film). Despite these unfavorable facts, we think that if the multi-layered [NB60-x](n), or [CxB60-x](n) film could be formed, it is possible to find the optimal sample, with either the composition X-A(0) or X-C(0), which exhibits good MR sensitivity S, while at the same time zero lambda(s). Indeed, we found that: (1) when X-A(0) = 50 nm, S can be as high as 1.9%/Oe, and (2) when X-C(0) = 35 nm, S is 0.40%/Oe. More importantly, we have shown that T-s = 340 degreesC is the best choice for the [A/B] multilayers, when a more precise control Of x(A) is required in order to get the linear dependence of lambda(s) on x(A). (C) 2004 Elsevier Ltd. All rights reserved.