Perpendicular magnetic anistropy in Co2FeAl thin films: Effect of the annealing temperature

Abstract

Perpendicular magnetic anisotropy (PMA) is considered as one of the highly desirable properties of magnetic thin films for modern spintronic devices. In fact, the integration of materials with PMA reduces the critical current densities and enhances the thermal stability [1] in spin transfer torque based magnetic random access memories (STT-MRAM). Moreover, the large anisotropy values in such materials yields narrow domain walls making them good candidates for high-density STT-MRAM involving the propagation of magnetic domain walls. Co/Pt and Co/Pd mutilayers have been recognized many years ago as perpendicularly magnetized materials [2]. However, their application as electrodes in magnetic tunnel junctions (TMJ) and in giant magnetoresistance (GMR) devices has been limited by the reduced magnetoresitsance (TMR or GMR) values [2] and the high Gilbert damping parameter due to the spin-orbit coupling (SOC) of the Pt or Pd. Recently, strong PMA in ferromagnetic thin films (FM), Co, CoFe, and CoFeB when interfaced with an oxide, has been demonstrated [3-5] due to the hybridization of the O 2p and the FM (e.g. Fe) 3d orbitals, together with a degeneracy lift induced by SOC. Therefore, designing heterostructures presenting this interface PMA and incorporating FM that combines high spin polarisation and low Gilbert damping such as Co 2 FeAl (CFA) full Heusler alloy would be an attractive step towards building suitable materials for the above-mentioned spintronic applications.