Effective magnetic anisotropy field of Pd/Ni multilayers

Abstract

The effective magnetic anisotropy field of Pd/Ni multilayer structures has been investigated. The strain between the substrate and magnetic thin film may contribute significantly to the effective internal field via magnetostriction since Ni is a strong magnetostrictive ferromagnet. The multilayer structures with Ni thicknesses larger than the exchange length (3.2 nm) were studied by means of FMR at the X-band. Polycrystalline samples were deposited (rf-sputtered) on Corning glass and mica. FMR measurements yield an effective anisotropy field including various anisotropy contributions; in our case we have the magnetic shape anisotropy field H u, the stress-induced anisotropy field H σ and the magnetic interaction field H int· H σ was found to be dependent on the Ni thickness, but was not altered by the thicknesses t 1 and t 2 of Pd for Pd( t 1)/Ni and Pd( t 1)/Ni/Pd( t 2) structures. The magnetic interaction field H int in the Pd( t 1)/Ni/Pd( t 2)/Ni/Pd( t 3) structure versus the thickness t 2 of the Pd interlayer (the middle layer) is also altered by stresses. For each value of t 2 (from 1.0 to 5.0 nm) H int of a more strained film (Corning glass as the substrate) is smaller than that for a less strained one (mica as the substrate). The surface mode excitations in the spin wave resonance (SWR) experiment were used to derive the surface anisotropy energy constant K s. For the Pd( t 1)/Ni/Pd( t 2)/Ni/Pd( t 3) structure, K s is altered by stresses but does not depend on the thickness t 2 of the Pd interlayer.