Effect of the structure and thickness of layers on the magnetic and magnetoresistive properties of Py/Co/Cu/Co nanocrystalline films

Abstract

Py/Co1/Cu/Co2 films (Py is the Ni63Co25Fe12 ternary permalloy) were produced by magnetron sputtering on glass substrates. The thicknesses of layers are d Cu = 0.7–4 nm, $$d_{Co_2 } $$ = 2–12 nm, and d Py = 2–12 nm. The polar diagrams of the films with d Cu = 1.2nm demonstrate a biaxial anisotropy, whereas the films with 2.0 ≤ d Cu ≤ 3.0 nm are characterized by uniaxial anisotropy. The first maximum in the Δρ/ρ = f(d Cu) curve is due to an antiferromagnetic coupling between the Py/Co1 and Co2 layers; the second maximum is due to the independent magnetization reversal of the Py/Co1 soft magnetic bilayer and Co2 hard magnetic layer. The magnetoresistance measured along the EA exhibits an almost twofold increase with increasing thickness of ferromagnetic layers. The coercive force was shown to decrease with increasing thickness of the Co2 layer, whereas the magnetic anisotropy field is unchanged. The coercive force and induced magnetic anisotropy were estimated theoretically taking into account changes in the mean-square amplitude and roughness period with increasing thickness of the Co2 layer. The results obtained agree with experimental data.