Thermoelectric Characteristics of STE Generator Fabricated From LPE Bi- and Al-Substituted YIG Films

A spin thermoelectric (STE) generator is composed of a thin paramagnetic metal (PM) layer, ferrimagnetic insulator (FMI) and PM/FMI bilayer interface. Various studies have been carried out on improving the characteristics of each part of this structure in order to raise the STE voltage
$V_{\mathrm {STE}}$
. We investigated the substitution of bismuth for yttrium and aluminum for iron to observe the characteristic changes in
$V_{\mathrm {STE}}$
. FMI films of epitaxial Bi-substituted iron garnets exhibit large growth-induced magnetic anisotropy perpendicular to the film surface. This anisotropy increases the magnetic damping
$\alpha $
in the FMI, and the values of
$\alpha $
increase with increasing Bi content. As a result, a large rise in STE voltage was observed. We report the rise in
$V_{\mathrm {STE}}$
observed in an STE generator incorporating Bi-substituted yttrium iron garnet (YIG) films grown by liquid phase epitaxy (LPE) and explain the origin of the voltage rise based on the results of ferromagnetic resonance measurements. To comprehensively examine the effect of substitution on LPE YIG films, the
$V_{\mathrm {STE}}$
values observed in STE generators incorporating Al-substituted YIG films are also presented.