(a) Schematic diagram of the crystal structure of antiferromagnetic CrO. (b) Cross-sectional transmission-electron microscopy image of the YIG/CrO/Pt trilayer device used in this research. Scale bar represents 5 nm. Easy axis c of CrO is in the film’s out-of-plane direction z. (c) External magnetic field H dependence of voltage signal V measured in YIG/Pt bilayer device at 300 K. (d) External magnetic field H dependence of voltage signal V measured in YIG/CrO/Pt trilayer device at various temperatures. (e) Temperature dependence of spin Seebeck voltage V_SSE at H=0.1 T for YIG/CrO/Pt trilayer device. Inset shows concept of spin-current transmissivity measurement. (f) Temperature dependence of spin Seebeck voltage V_SSE at H=0.1 T for a YIG/Pt bilayer device. (g) Temperature dependence of spin pumping signals V_ISHE for YIG/Cr₂O₃/Pt trilayer devices with various values of Cr₂O₃ layer thickness d Cr 2 O 3 . (h) Temperature dependence of spin Seebeck voltage V_SSE at H=0.1 T for YIG/Cu/CrO/Pt and CrO/Pt devices.