Scaling of the Thermally Induced Sign Inversion of Longitudinal Spin Seebeck Effect in a Compensated Ferrimagnet: Role of Magnetic Anisotropy

Abstract The authors report on a systematic investigation of the longitudinal spin Seebeck effect (LSSE) in a GGG(Gd₃Ga₅O₁₂)/GdIG(Gd₃Fe₅O₁₂)/Pt film series exhibiting an in‐plane magnetic easy axis with a compensation temperature (T_Comp) that decreases from 270 to 220 K when decreasing GdIG film thickness from 272 to 31 nm, respectively. For all the films, the LSSE signal flips its sign below T_Comp. The authors demonstrate a universal scaling behavior of the temperature dependence of LSSE signal for the GdIG films around their respective T_Comp. Additionally, the authors demonstrate LSSE in a 31 nm GdIG film grown on a lattice‐mismatched GSGG (Gd₃Sc₂Ga₃O₁₂) substrate that exhibits an out‐of‐plane magnetic easy axis at room temperature. However, this sample reveals a spin reorientation transition where the magnetic easy axis changes its orientation to in‐plane at low temperatures. A clear distinction is observed in the LSSE signal for the GSGG/GdIG(31 nm)/Pt heterostructure, relative to GGG/GdIG(31 nm)/Pt showing an in‐plane magnetic easy axis. The findings underscore a strong correlation between the LSSE signal and the orientation of magnetic easy axis in compensated ferrimagnets and opens the possibility to tune LSSE through effective anisotropy.