Interlayer coupling across semimetallic iron monosilicide

Abstract

We studied the interlayer exchange coupling between Fe films across iron monosilicide spacer layers with the metastable CsCl structure. The bilinear $({J}_{1})$ and the biquadratic $({J}_{2})$ coupling strengths are determined by fitting the in-plane easy- and hard-axis magnetization curves. Both coupling coefficients have a strong, nonmonotonous temperature dependence and vary exponentially as a function of the spacer thickness. The temperature dependence of the coupling constants is explained within the framework of Slonczewski's loose spin model [J. Appl. Phys. 73, 5957 (1993)] in which a decrease of the loose spin concentration upon cooling is introduced. The exponentially decaying coupling strength with increasing spacer layer thickness is attributed to the semi-metallic nature of the metastable monosilicide phase.