Spin-to-heat current conversion effects have been investigated in bilayer films consisting of a paramagnetic metal (PM; Pt, W, or Ta) and a ferromagnetic metal (FM; CoFeB or permalloy). When a charge current is applied to the PM/FM bilayer film, a spin current is generated across the PM/FM interface owing to the spin Hall effect in PM.The spin current was found to exhibit cooling and heating features depending on the sign of the spin Hall angle of PM, where the spin-current-induced contribution is estimated by subtracting the contribution of the anomalous Ettingshausen effect in FM monolayer films. We also found that the magnitude of the spin-current-induced temperature modulation in the Pt/CoFeB film is greater than but comparable to that in the Pt/permalloy film, although the spin dependence of the Peltier coefficient for CoFeB is expected to be greater than that for permalloy.We discuss the origin of the observed behaviors with the aid of model calculations; the signals in the PM/FM films may contain the contributions not only from the electron-driven spin-dependent Peltier effect but also from the magnon-driven spin Peltier effect.

The spin Seebeck effect (SSE), the generation of a spin cur rent as a result of a temperature gradient in a magnetic mat erial, triggered intense research on spin caloritronics [1][2][3][4][5][6][7][8]. By attaching a conductor to the magnetic material, the spin current induced by the SSE can be detected by means of the inverse spin Hall effect (ISHE) [9][10][11][12]. Most SSE experiments to date have been performed by using Pt/yttriumirongarnet (YIG) hybrid systems [4][5][6][13][14][15][16], and this phenomenon is explained in terms of nonequilibrium thermal magnon transport [17][18][19][20]. Recently, the SSE has been observed also in a magneticallycompensated ferrimagnetic insulator, gado linium iron garnet (GdIG) [21,22]. In the temperature depend ence of the SSE for Pt/GdIG systems, two sign changes of the SSE signal have been observed at the magnetization com pensation temperature of GdIG and at the temperature where the heattospin current conversion efficiency from different magnon branches competes with each other [21][22][23]. This result demonstrates that the SSE in a compensated ferrimagn etic insulator is sensitive to the magnon dispersion relation.The spin Peltier effect (SPE), the reciprocal effect of the SSE, refers to the heatcurrent generation as a result of a spin

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