Andreev reflection and incoherent spin-polarized transport in ferromagnetic semiconductor/d-wave superconductor/ferromagnetic semiconductor tunnel junctions with {110} interfaces

The hole spin accumulation and spin-polarized transport in ferromagnetic semiconductor (FS)/d-wave superconductor (SC)/FS tunnel junctions with (110) interfaces are studied by using four-component Bogoliubov-de Gennes equations, in which the Andreev reflection and four-subband model for the FS are taken into account. It is found that due to the interplay of the d-wave SC and FS, the nonequilibrium hole spin accumulation, differential conductance, and tunneling magnetoresistance exhibit a rich dependence on the Andreev reflection, strengths of potential scattering at the interfaces, mismatches in the effective mass and band between the FS and SC, and types of incident holes, which is much different from that in FS/s-wave SC/FS tunneling junctions. Particularly, it is demonstrated that the differential conductance can be negative in both ferromagnetic and antiferromagnetic alignments for not only incident heavy holes but also incident light holes, and the variations in both the energy gap with temperature and hole spin accumulation with bias voltage can display a twofold behavior due to the Andreev reflection. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3410926]