Preparation of Ni–Fe/Cu multilayers with low coercivity and GMR effect by ion beam sputtering

Abstract

Multilayers composed of 30 [Ni–Fe/Cu] bilayers deposited on a 50-Å-thick Fe buffer layer were prepared by ion beam sputtering. The magnetoresistance (MR) ratio Δρ/ρ0 of the multilayers took high value at the Cu layer thickness δCu of 10, 20, and 32 Å for the multilayers with Ni–Fe layer thickness δNi–Fe of 10 Å. It was observed that (100) orientation of Ni–Fe and Cu crystallites were enhanced at δCu of 20 and 32 Å. The multilayered film with δCu of 10 Å exhibited Δρ/ρ0 as high as 12%. The multilayered film possessed good soft magnetic properties, and exhibited coercivity Hc and relative permeability μr of about 4 Oe and 800, respectively. The saturation magnetic field Hs was about 300 Oe. Δρ/ρ0, Hc, and Hs at δCu of 20 Å, i.e., at the ‘‘second peak,’’ were 6%, 10 Oe, and 25 Oe, respectively. The δCu dependence of Δρ/ρ0 seemed to be correspondent to that of the preferential orientation of the (100) plane. Ni–Fe/Cu multilayers with the same construction but without an Fe buffer layer did not reveal apparent (100) preferential orientation and did not exhibit Δρ/ρ0 as high as detectable. Then, Δρ/ρ0 was strongly dependent not only on interlayer thickness, such as δCu, but also (100) crystallite orientation.