Test of unified picture of spin-dependent transport in perpendicular (CPP) giant magnetoresistance and bulk alloys

Measurements of current perpendicular (CPP) magnetoresistance (MR) on hybrid and exchange-biased spin valves allow determination of the layer anisotropy parameter beta for ferromagnetic alloys, thus allowing testing of whether this CPP beta is similar to values obtained from direct measurements on, and theoretical estimates for, dilute bulk ferromagnetic alloys. Of special interest are alloys where beta is expected to be negative. In this article, we derive a value of beta for a Ni97Cr3 alloy using such spin valves based upon permalloy. We confirm prior CPP-MR results that this beta is negative, but our inferred value, beta=-0.35+/-0.1, is closer to bulk and theoretical estimates. Our data thus provide new support for a unified picture of beta in the CPP-MR and bulk alloys. We also derive a short spin-diffusion length in NiCr, l(sf)=3+/-1 nm. (C) 1999 American Institute of Physics. [S0021-8979(99)19108-4].