Impact of Boron doping to the tunneling magnetoresistance of Heusler alloy Co₂FeAl

Co-based Heusler alloys as Co₂FeAl (CFA) have been of noteworthy interest for Magnetic Tunnel Junctions (MTJs) due to having high curie temperature, high spin polarization, and low damping coefficient. High Tunneling Magneto Resistance (TMR) values usually are obtained from epitaxial CFA MTJs deposited at high temperature on a MgO seed-layer or MgO substrate. In this work, the deposition is done at room temperature on a conventional thermally oxidized silicon wafer without a seed-layer. The epitaxial structure of ferromagnetic electrodes along with the insulating barrier is obtained by solid state epitaxy through the crystallization of MgO during post-deposition annealing, which is a critical step to form the symmetry-conserved coherent tunneling channels. Surface roughness and the crystal structure is improved and hence an enhancement of TMR is observed through the incorporation of B in the Co₂FeAl electrodes. This work is supported by NSF and DARPA.