Exchange anisotropy in MBE grown MnPt/NiFe bilayers

Abstract

Exchange anisotropy has been investigated by torque magnetometry for MnPt(30 nm)/NiFe(5 nm) bilayers grown by the MBE method on MgO[001], SrTiO/sub 3/[001], and MgO[111] substrates. In-situ reflection high-energy electron diffraction observation and ex-situ X-ray diffraction measurements revealed that the MnPt layers have chemical order and have [100] uncompensated and [111] compensated plane parallel to the film plane, respectively for [001] and [111] substrate orientation. In MnPt/NiFe/SrTiO/sub 3/[001] torque components of unidirectional and uniaxial anisotropies have been observed, while in NiFe/MnPt/MgO[001] both the anisotropies almost disappeared and a torque curve with four fold symmetry was observed. This torque curve seems to be closely related with the crystal anisotropy of MnPt.