Noncollinear ferromagnetic easy axes in Py/Ru/FeCo/IrMn spin valves induced by oblique deposition

We present an investigation on the magnetic properties of Py/Ru/FeCo/IrMn spin valves grown by dc magnetron sputtering. The sample fabrication setup has two important features, (i) the five magnetron sputtering sources are placed in a cluster flange 72° from each other, and (ii) each source is tilted with respect to the sample normal. In-plane angular dependence of the ferromagnetic resonance (FMR) was used to obtain the relevant magnetic anisotropies, such as uniaxial and exchange bias fields. The oblique deposition geometry employed has induced non-collinear easy axes of the two ferromagnetic (FM) layers, with high uniaxial field strengths. The symmetry shift of the angular dependence of the FMR resonances of the two FM layers gives us directly the angle between the easy axes of FM₁ (Py) and FM₂ (FeCo), which turned out to be the angle between two adjacent sputtering sources. The observations of the present study suggest that, by combining oblique deposition and appropriate angles of incidence of the deposition flux, the uniaxial (and unidirectional) axes of individual FM layers can be precisely engineered in spin valve fabrication.