Noncollinear interlayer exchange coupling across IrFe spacer layers

In this paper, we show that IrFe spacer layers enable the control of noncollinear interlayer exchange coupling between ferromagnetic Co layers over a spacer layer composition and thickness range that is larger than any observed before for other spacer layer materials. Moreover, in the studied Co|IrFe|Co structures, the bilinear coupling strength, J1, is above 2 mJ/m2 and the biquadratic coupling strength, J2, is above 1 mJ/m2 over a wide spacer layer composition and thickness range. Notably, the largest antiferromagnetic bilinear coupling strength ever observed across spacer layers of 0.6 nm or thicker is achieved, with J1 peaking at 3.4 mJ/m2. After annealing, orthogonal coupling is favoured over a wide spacer layer composition and thickness range, which could be useful for magnetic sensor devices. As the temperature is reduced below room temperature, the coupling parameters of the as-deposited films vary slowly, which could be a desirable feature for applications. Measurements of the saturation magnetization of Co|IrFe|Co structures reveal that IrFe has a magnetic moment in the spacer layer composition range for which noncollinear coupling is observed. This indicates that the origin of noncollinear coupling in Co|IrFe|Co could be attributed to the competition between the antiferromagnetic coupling of magnetic atoms across Ir atoms in the spacer layer and the ferromagnetic coupling of neighbouring magnetic atoms.