First-principles study of anomalous and spin Hall conductivities in Fe/MgO superlattices with transition-metal insertions

摘要

Hall effects have found applications in spintronic devices.Inferromagnetic material the Hall resistivity is proportional to the magnetization. This phenomenonis the anomalous Hall effect (AHE) which has important roles in the investigation and characterization of ferromagnetic materials. The spin Hall effect (SHE) and its inverse have been used to generate and detect the spin current in non-magnetic materials.Additionally,the SHE tunneling spectrahave been considered to provide guidelines for engineering high-SHE materials.It isimportant toelucidate the magnetic transport propertiessuch as AHE and SHE in the tunnel junctions.Here, in order to systematically investigate the magnetic transport properties as well as the effect of the geometrical and magnetic structures, we have performed magnetic transport calculation method by using full-potential linearized augmented plane-wave (FLAPW) method within a superlattice model,and discussed the effectof the insertions of heavy metals such as 4d and 5d transition-metal at the Fe/MgO interfaceto the magnetic transport properties.Self-consistent calculations were carried out based on the generalized gradient approximation, and the transport coefficients were evaluated using the Kubo formulations. For the Fe/MgO (assumingseveral atomic-layers of MgO)with onemonolayer of 4d(Ru, Rh, Pd) and 5d(Os, Ir, Pt)metals inserted at the Fe/MgO interface,wesystematically investigatedthe anomalous and spin Hall conductivities along the film normal.Our results show that the anomalous Hall conductivity (AHC) is enhanced due to the insertion.The spin Hall conductivity (SHC) is also enhanced, andthe magnitudesof SHC become largewhen5dtransition-metalelements are inserted. An analysis of the electronic structures for theorigin of the AHC and SHC enhancement by the insertions will bepresented.