Anisotropic magnetothermopower: Contribution of interband relaxation

Abstract

Spin injection in metallic normal/ferromagnetic junctions is investigated taking into account the anisotropic magnetoresistance occurring in the ferromagnetic layer. On the basis of a generalized two-channel model, it is shown that there is an interface resistance contribution due to anisotropic scattering, besides spin accumulation and giant magnetoresistance. The corresponding expression of the thermoelectric power is derived and compared with the expression accounting for the thermoelectric power produced by the giant magnetoresistance. Measurements of anisotropic magneto-thermoelectric power are presented in electrodeposited Ni nanowires contacted with Ni, Au, and Cu. It is shown that this thermoelectric power is generated at the interfaces of the nanowire. The results of this study indicate that, while the giant magnetoresistance and the corresponding thermoelectric power indicate the role of spin-flip scattering, the observed anisotropic magneto-thermoelectric power might be the fingertint of interband s-d relaxation mechanisms.

Anomalous Nernst effect in Ir22Mn78/Co20Fe60B20/MgO layers with perpendicular magnetic anisotropy

“…A branch of spintronics called spin caloritronics [1][2][3][4][5][6][7][8][9][10][11][12][13] focuses on the interplay of spin and heat currents. The effects discovered in this emerging research field have revived interest in the anomalous Nernst effect (ANE), which is defined as the voltage observed perpendicular to both the heat current and the spontaneous magnetization.…”

Spin-Currents and Spin-Pumping Forces for Spintronics

“…Δμ s (18) where the four diffusion lengths {l sd , λ s , l sf , λ sd } are given as a function of the transport coefficients in reference [24]. The resolution of the coupled diffusion equations (the spin-accumulation processes) is discussed in the same reference.…”

“…The set of equations Equation (9) is sufficient in order to describe, in the stationary regime, spin-accumulation effects and any non-equilibrium contribution to the resistance due to relaxation (Δμ = 0) occurring at an interface [18,24]. Equation (9) shows that the spin-dependent electric currents J e and the spin fluxψ are not independent.…”

“…The corresponding non-equilibrium magnetoresistance produced by the interface writes (see the details of the derivation in references [18,24,46]):…”

“…We have then a four-channel model, in which two kinds of spin fluxψ andψ sd should be defined for both interband and intraband spin-dependent relaxation. A third kind of pumping force can then be introduced with the interband chemical potential difference Δμ sd [18]. This treatment is performed in Section 5.…”