First-principles investigation of spin-dependent thermoelectric transport and spin Seebeck in Fe(110)/Co($$11\bar{2}0$$) heterostructures

We compute spin-dependent thermoelectric properties of Fe(110)/Co([Formula: see text]) thin films using spin-polarized density functional theory combined with semiclassical Boltzmann transport. The spin-resolved Seebeck coefficients [Formula: see text] and [Formula: see text] remain negative and metallic, with magnitudes of a few tens of [Formula: see text] between 0 and 500 K and only weak sensitivity to small rigid-band dopings. Because the transport formalism yields [Formula: see text], we estimate the relaxation time using two complementary models, namely an acoustic-phonon-limited deformation-potential approach and an empirical metallic lifetime inferred from the Seebeck coefficient. The former gives sub-picosecond to picosecond lifetimes, while the latter yields shorter lifetimes of a few tens to a few hundred femtoseconds. The resulting conductivities fall in a realistic thin-film range and show clear in-plane anisotropy with [Formula: see text], reflecting anisotropic band velocities and effective masses. Within a two-current description, the spin Seebeck coefficient [Formula: see text] reaches a few [Formula: see text] with deformation-potential lifetimes but is reduced to a directional average of about [Formula: see text] at 300 K when empirical lifetimes are used. These values provide a baseline estimate of the effective electronic contribution within the two-current framework for all-ferromagnet Fe/Co stacks.