High-field anisotropy of the tunnelling magnetoresistance of CoFeB/MgO/CoFeB junctions

Abstract Differential resistance data is gathered on both as-deposited and annealed tunnel junctions based on CoFeB/MgO interfaces, where one of the layers is pinned via exchange bias. When sufficiently strong magnetic field is rotated out of the plane of the junctions, a characteristic bias dependence of the anisotropic term in the differential resistance is observed at low temperature and all fields (from 5–14 T), which may be represented by a voltage dependent base function A ( V ) together with an angular sin 2 ( θ + ϕ ) dependence, where θ is the angle between the normal to the plane of the junction and ϕ is an offset phase. The base function reflects the anisotropy in the spin-polarized density of states of crystallized CoFeB and its spin-resolved Fermi surfaces.