Evaluation and study of spin Seebeck effect in Pt/Y 3 Fe 5 O 12 /Gd 3 Ga 5 O 12 and Pt/Y 3 Fe 5 O 12 /sapphire systems

Utilization of the spin Seebeck effect, a method for obtaining clean natural energy, is attracting more and more attention. We investigated the spin Seebeck voltage in relation to the saturation magnetization in yttrium iron garnet (YIG). We found that it is not proportional to saturation magnetization in YIG, indicating the existence of spin-current conductance in YIG. Pt/YIG samples with the same interface roughness and different structures exhibited different spin Seebeck voltages. The difference in the minimum YIG thicknesses for the saturation of the spin Seebeck voltage of Pt/YIG/gadolinium gallium garnet and Pt/YIG/sapphire structures was estimated on the basis of the relationship between the proportionality constant and the thickness dependence. The crystallinity of the YIG on these two substrates was investigated by X-ray diffraction spectrum observation. The spin-current conductance in Pt/YIG/substrates was found to be affected by the crystallinity of the YIG films.