Temperature-dependent spin thermopowers in Pt/Ni80Fe20/Al2O3 heterostructures via the longitudinal spin seebeck effect

초록

The longitudinal spin Seebeck effect (LSSE) arises when a temperature gradient applied across a magnetic insulator generates a spin current, which is subsequently converted into an electric voltage in an adjacent normal metal (NM) via the inverse spin Hall effect (ISHE). Although NM/ferromagnet heterostructures such as Pt/Ni80Fe20 are promising platforms for investigating spin caloritronic phenomena, detailed studies of LSSE at low temperatures remain limited. Here, we investigate the temperature dependence of LSSE in Pt/Ni80Fe20 films on Al2O3 substrates over a temperature range from room temperature down to 50 K, revealing the evolution of magnetic and spin–thermoelectric properties in the low-temperature regime. By independently quantifying the proximity-induced anomalous Nernst effect (ANE) of Pt/Ni80Fe20 films, we identify a notable contribution from this effect, accounting for approximately 3–18% of the measured LSSE spin thermopower. Furthermore, we theoretically calculate the temperature-dependent LSSE voltage using both a conventional Boltzmann transport model and Landau–Lifshitz–Gilbert (LLG) dynamics, obtaining good agreement with the experimental results for the Pt/Ni80Fe20 structure. These findings underscore the significant role of the proximity-induced ANE in LSSE measurements and provide new insights into spin–thermal transport in metallic ferromagnetic heterostructures.

키워드