Exchange coupling of NiFe/FeRh–Ir thin films

Abstract

We report unusually large room temperature coercive field Hc induced in Ni0.81Fe0.19 films grown on the (001) magnetically compensated surface of antiferromagnetic single crystal CsCl-type FeRh0.95Ir0.05 alloy thin layers on MgO(001) substrates. The specimens were prepared by conventional rf sputtering in Kr atmosphere, at 450–500 °C for FeRh–Ir and 20–200 °C for NiFe. The epitaxial growth of NiFe/FeRh–Ir and atomically flat terraces of FeRh–Ir were confirmed by x-ray reflectometry and scanning tunneling microscopy. For a NiFe(2.7 nm)/FeRh–Ir(22 nm) film, a maximum Hc of 810 Oe is observed. The 1/tNiFe dependence of Hc for larger NiFe thicknesses indicates that the large coercive field originates from the magnetic interaction at NiFe/FeRh–Ir interface. The large Hc combined with high corrosion resistance make FeRh based alloys a promising candidate for application as pinning layers in spin-valve devices.