Current-perpendicular spin valves with high-resistivity ferromagnetic metals for ultrahigh-density magnetic recording

We have observed a large specific magnetoresistance change (ΔRA, product of resistance change and element area) in metallic spin valves in the current-perpendicular-to-plane (CPP) mode by employing ferromagnetic Co-Fe-Al alloys as free and reference layers. The ΔRA is about five times larger than that for conventional materials. The results were analyzed with the semiclassical two-current theory, and the enhancement in ΔRA is ascribed to compatibility of relatively high resistivity and a large spin-asymmetry coefficient for the spin-dependent bulk scattering of the alloys. Since half-metallicity is not always necessary to realize such properties, this opens up new ways of developing CPP spin valve materials. The alloys show, respectively, low coercivity and high effective pinning field as the free and reference layers, which are eminently suitable for their practical application to a magnetic read sensor. Their applicability to the read heads for over 300 Gbit/in2 recording density is also discussed.