Magnetic anisotropies in single and multilayered thin films grown by bowed-substrate sputtering

Thin-film structures composed of nearly nonmagnetostrictive single-layer Co₇₆Fe₄B₂₀ or magnetostrictive Fe₈₀B₂₀ and Co₇₅Si₁₅B₁₀ amorphous layers have been deposited on bowed glass substrates using the RF-sputtering technique. The fabrication procedure induces a postdeposition compressive stress in the thin-film structure when the sample is retrieved from an arching device in the sputtering chamber. This results in an induced magneto-elastic anisotropy that governs the magnetic easy axis of the film, depending on the sign of the magnetostriction constant of each layer. Particular attention is paid here to heterogeneous structures made of bi- or multilayers with magnetic easy axis oriented in a different direction in each layer. Bulk magnetic properties were evaluated from hysteresis loops and thermomagnetization measured by vibrating sample magnetometry (VSM) and quantum interference device (SQUID) magnetometry. Magnetic domain walls and out-of-plane magnetized domains were observed by a Kerr imaging system and magnetic force microscopy. The combination of microstructure and strains induced in the layers determines the orientation of the observed magnetic anisotropies, which vary from high in-plane anisotropies up to out-of-plane orientations for selected films. The results, which provide reassurance that effective anisotropies are induced in each of the layers, are discussed in terms of the interactions between magnetic phases with different induced easy magnetization axes