Interplay of growth mode and thermally induced spin accumulation in epitaxial Al/Co2_2TiSi/Al and Al/Co2_2TiGe/Al contacts


The feasibility of thermally driven spin injectors built from half-metallic Heusler alloys inserted between aluminum leads was investigated by means of {\em ab initio} calculations of the thermodynamic equilibrium and electronic transport. We have focused on two main issues and found that: (i) the interface between Al and the closely lattice-matched Heusler alloys of type Co2_2TiZZ (Z=Z= Si or Ge) is stable under various growth conditions; and (ii) the conventional and spin-dependent Seebeck coefficients in such heterojunctions exhibit a strong dependence on both the spacer and the atomic composition of the Al/Heusler interface. The latter quantity gives a measure of the spin accumulation and varies between +8+8~μ\muV/K and 3-3~μ\muV/K near 300300~K, depending on whether a Ti-Ge or a Co-Co plane makes the contact between Al and Co2_2TiGe in the trilayer. Our results show that it is in principle possible to tailor the spin-caloric effects by a targeted growth control of the samples.Comment: 16 pages, 13 figure

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