Cu(50 Å)/NiFe(60 Å)/Cu(60 Å)/Co(20 Å) epitaxial spin-valve structures were grown on GaAs(001) substrates by molecular-beam epitaxy at room temperature. In situ reflection high-energy electron diffraction measurements indicate the stabilization of the bcc-Co(001) phase on 1×1 unreconstructed GaAs(001) for thicknesses up to 20 Å and the epitaxial growth of the fcc-Cu(001) spacer layer and fcc-FeNi(001) top magnetic layer. Magneto-optical Kerr effect and Brillouin light-scattering measurements of the composite structure showed that a fourfold cubic anisotropy is present but a twofold anisotropy also occurs directed along the 〈110〉 axes. The easy cubic axes are directed along the 〈100〉 axes, which implies that the cubic anisotropy constant Kl for bcc-Co is positive. The magnetic anisotropy of the bcc-Co layer has a striking influence on the magnetoresistance characteristics which were found to be angular dependent. A simulation of this mixed anisotropy behavior yields quantitative agreement with the experimental results.

Asymmetric hysteresis loops are generally found in exchange-coupled ferromagnetic/antiferromagnetic layers or composite. Once the film is deposited the magnetization reversal behaviour becomes certain due to the fixed anisotropy of the film. We report an asymmetric magnetization reversal, which is erase/restorable in polycrystalline soft magnetic film. When the film is pre-saturated at a high field in the induced uniaxial easy direction, the asymmetric hysteresis loops with one branch governed by "coherent rotation" and another branch with kink induced by mixed reversal mechanism of "coherent rotation" and "rotation/180 degrees-domain-wall-motion/rotation" are obtained. If the film is presaturated in the induced hard axis, the kink disappears and "normal" hysteresis behaviour is observed instead. Such asymmetric magnetization curve can be restored if the film is pre-saturated in the easy axis again. The observed phenomenon is originated from an embedded second magnetically hard phase which tunes the anisotropy in the film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4765652