Exchange coupling of a perpendicular ferromagnet to a half-metallic compensated ferrimagnet via a thin hafnium interlayer

A thin Hafnium film is shown to act both as an effective diffusion barrier for manganese at a thickness of 0.7 nm and as an effective exchange coupling layer in a sandwich structure with perpendicular magnetic anisotropy. The two magnetic layers are Co20Fe60B20 and the low moment ferrimagnet Mn2RuxGa (MRG). The relative orientation of the magnetic layers changes sign at the compensation temperature of MRG. The exchange energy reaches 0.11 mJ m(-2) for the thinnest Hf interlayers. Ruthenium, the usual metal of choice for coupling ferromagnetic layers in thin film heterostructures, cannot be used with the zero-moment half metal MRG because of Ru interdiffusion. Due to its large coercivity near compensation, the MRG can potentially act as an effective source of exchange pinning. Published by AIP Publishing.