Surface spin reorientation in thin Gd films on Fe in an applied magnetic field

Abstract

We investigate the magnetic system of a few layers of Gd on bulk Fe in the presence of a magnetic field using mean-field theory and a simple model. At moderate temperatures and low fields the system is in an aligned state where all the Fe spins point along the field direction and, because of the antiferromagnetic coupling of the Fe spins to the Gd spins, all the Gd spins are antiparallel to the field. For higher fields there is a phase transition to a twisted spin state where the Fe and Gd spins near the interface are at an angle with respect to the applied field.