The influence of Cu spacer morphology in Cu/Py/Cu/Co/IrMn spin valves with induced non-collinear spin structures

Abstract

Non-collinear exchange couplings between Py and Co layers (0°⩽φ⩽90°) were achieved in Py(10)/Cu(5)/Co(10)/IrMn(8) (thickness values in nm) spin valves by modifying their layer morphologies using oblique deposition in a confocal sputtering setup. Two series of spin valves were prepared by keeping the sample holder fix during the depositions, except for the Cu spacers that were deposited using either fixing (Series-I) or spinning mode (Series-II). Series-I (Series-II) has Cu spacer layers composed by oriented (non-oriented) grains and Cu/Co interfacial roughnesses relatively rougher (smoother), favoring lower (higher) interlayer exchange couplings and exchange bias fields. The magnetization easy axis of Py and the unidirectional anisotropy axis followed the expected directions, while the Co uniaxial axis is surprisingly dephased by (15±5)° for 0°⩽φ<90°. The angular offset between the Co uniaxial axis and the Py uniaxial (unidirecional anisotropy) axis was more pronounced in Series-I, indicating that the Cu spacer roughness played an important role in the interlayer exchange couplings and also in the Co spin reorientation effect. The magnetoresistance magnitudes were similar to those found in the literature for ordinary Py/Cu/Co multilayers. However, it reduces as the φ-angle increased, an effect associated with the enhancement of the interface roughness due to the misalignment of the oriented grains of adjacent layers.