Spin-dependent thermoelectric effects in transport through a nanoscopic junction involving spin impurity

TL;DR

This paper theoretically investigates spin-dependent thermoelectric effects in magnetic tunnel junctions with a large-spin impurity, revealing how magnetic anisotropy influences electron spin reversal and thermoelectric properties.

Contribution

It introduces a detailed theoretical model incorporating magnetic anisotropy to analyze spin and thermoelectric effects in impurity-involved tunnel junctions, highlighting mechanisms for pure spin current generation.

Findings

Spin reversal during tunneling due to transverse magnetic anisotropy.

Dependence of Seebeck and spin Seebeck coefficients on impurity parameters.

Pure spin current can be driven without electron transfer, via impurity-mediated processes.

Abstract

Conventional and spin-related thermoelectric effects in transport through a magnetic tunnel junction with a large-spin impurity, such as a magnetic molecule or atom, embedded into the corresponding barrier are studied theoretically in the linear-response regime. The impurity is described by the giant spin Hamiltonian, with both uniaxial and transverse magnetic anisotropy taken into account. Owing to the presence of transverse component of magnetic anisotropy, spin of a tunneling electron can be reversed during scattering on the impurity, even in the low temperature regime. This reversal appears due to exchange interaction of tunneling electrons with the magnetic impurity. We calculate Seebeck and spin Seebeck coefficients, and analyze their dependence on various parameters of the spin impurity and tunnel junction. In addition, conventional and spin figures of merit, as well as the electronic contribution to heat conductance are considered. We also show that pure spin current can be driven by a spin bias applied to the junction with spin impurity, even if no electron transfer between the electrodes can take place. The underlying mechanism employs single-electrode tunneling processes (electrode-spin exchange interaction) and the impurity as an intermediate reservoir of angular momentum.