Finite temperature polarization in Co2MnSi-based magnetic tunnel junctions.

Hannes Allmaier

Institute of Theoretical and Computational Physics

H. Allmaier, N. Bucur, L. Chioncel, E. Arrigoni and E. Burzo Magnetic tunnel junctions containing the full Heusler half-metallic ferromagnet Co2MnSi shows a completely different finite temperature dependence of magnetization and polarization. We attribute this behavior to the existence of nonquasiparticle states above the Fermi energy. The origin of these states is connected to many-body interactions in which magnons play an important role. In order to minimize depolarization at finite temperatures a detrimental effect on magnonic excitations is required. A qualitative change of the magnonic branch can be obtained due to the presence of lanthanide impurities. Total energy calculations allow to evaluate the strength of the coupling between the rare-earth (4f) impurity spin and the manganese (3d) conduction electron spin. The calculated RE(4f)-Mn(3d) couplings indicate that rare-earths impurities are favorable candidates to minimize the finite temperature effects induced by the presence of magnonic excitations.