Surface magnetization thermal fluctuation driven anomalous behaviour of ordinary Hall effect in Pt/YIG

Abstract

The ordinary Hall coefficient (OHC) characterizes the electron diffusion and therefore is the essential prerequisite for rigorously acquiring the spin diffusion length and spin Hall angle in magnetic heterostructures that involves strong spin–orbit coupling. Here, OHC is investigated in Pt layers in contact with ferromagnetic insulating Y3Fe5O12 films. The OHC, being negative, abnormally increases in magnitude significantly with increasing temperature for ultrathin Pt layers whereas it shows negligible change for thick ones. Similar anomalous phenomena are observed for isoelectronic and ferromagnetic Ni films on paramagnetic Gd3Ga5O12 substrates. For Pt films on Gd3Ga5O12 substrates, however, the OHC always decreases in magnitude with increasing temperature. The anomalous behaviour of OHC in spin polarized Pt on Y3Fe5O12 and ferromagnetic Ni films is suggested to arise from significant changes of the Fermi level and the Fermi surface shape through combined effects of the magnetic proximity and the surface magnetization thermal fluctuation. The present work will facilitate the understanding of relaxation mechanism of pure spin current in Pt layers.