Spin-current phenomena at high magnetic fields and high temperatures

In the field of spintronics, many experimental and theoretical studies have been focused on spin-transport phenomena in paramagnet/ferromagnet junction systems, where a spin current plays a central role. After the first demonstration of spin transport in insulator-based systems [1], a Pt/YIG junction system becomes one of the prototype samples. In this system, itinerant spins in Pt and localized magnetic moments in YIG interact with each other via the interface s-d interaction, i.e., the spin-mixing conductance; this interaction is the basic mechanism underlying various spin-current-related phenomena, such as the spin pumping [1], the spin Seebeck effect [2], and the recently-discovered spin Hall magnetoresistance (SMR) [3]. In this talk, we report the observation of the longitudinal spin Seebeck effect (LSSE) [4] and the SMR in Pt/YIG systems at high magnetic fields and high temperatures. The LSSE measurements in a high magnetic field range confirm that the observed voltage in the Pt/YIG systems is of magnon origin, providing a useful way to distinguish the LSSE from the anomalous Nernst effect induced by proximity ferromagnetism in Pt [5]. The LSSE and SMR at high temperatures highlight the importance of the temperature dependence of the spin-mixing conductance at the Pt/YIG interface [6]. These results will be helpful for obtaining full understanding of the mechanism of the LSSE and SMR.\\[4pt] We thank E. Saitoh, S. Maekawa, G. E. W. Bauer, H. Adachi, Y. Ohnuma, T. Kikkawa, S. Daimon, Y. Shiomi, and J. Shiomi for their support and valuable discussions.\\[4pt] [1] Y. Kajiwara et al., Nature 464, 262-266 (2010). \newline [2] K. Uchida et al., Nature 455, 778-781 (2008), Nature Materials 9, 894-897 (2010). \newline [3] H. Nakayama et al., Phys. Rev. Lett. 110, 206601 (2013). \newline [4] K. Uchida et al., Appl. Phys. Lett. 97, 172505 (2010), J. Phys.: Condens. Matter 26, 343202 (2014). \newline [5] T. Kikkawa et al., Phys. Rev. Lett. 110, 067207 (2013), Phys. Rev. B 88, 214403 (2013). \newline [6] K. Uchida et al., Phys. Rev. X 4, 041023 (2014).