Fabrication Of Gd₃Fe₅O₁₂and Its Spin Transportation

Multiple-layer system with ferromagnetic insulator and non-magnetic metal has always been a hot topic for studying related effects in spintronics,such as spin pumping(SP),spin Hall magnetoresistance(SMR)and spin Seebeck effect(SSE).We choose yttrium iron garnet(YIG)and gadolinium iron garnet(GdIG)as spin current generators.By studying the similarities and differences of SMR and SSE,we demonstrate some deep understandings of the characteristics for spin current transport.This thesis mainly consists of the following two aspects:We use pulsed laser deposition system to grow high-quality YIG and GdIG thin films on which then platinum is deposited by sputtering.By comparing the SMR of YIG/Pt and GdIG/Pt at different temperatures,we discover the SMR of GdIG/Pt at low-T is distinctively smaller than which at high-T.This tells us the 4f electrons of Gd contribute to the spin-mixing conductance of the interface,which depends on temperature and is non-negligible at low-T.Negative SMR emerges in the vicinity of compensation point which we attribute to the canted phase of the magnetic moments of sub-lattices instead of collinear phase.Moreover,the magnetic moments of sub-lattices rotate as external magnetic field increases,resulting in the spin-flop,which the critical field is much smaller than in ordinary antiferromagnets.We also investigate the contribution of interface to SSE.We measure the SSE of YIG/Pt and GdIG/Pt at different temperatures.The SSE of YIG/Pt doesn't change its sign with the respect of temperature.In contrast,the SSE of GdIG/Pt changes its sign twice.By inserting GdIG between YIG and Pt,the SSE of this tri-layer system only change its sign at low T.By measuring M-T via SQUID-VSM,we exclude the transformation of magnetic structure and attribute this low-T change to the characteristic of GdIG as the interface,which plays the role of filtrating the spin current.After inserting YIG between GdIG and YIG,the SSE only change its sign at high-T which dues to change of magnetic structure of GdIG at compensation point.The sign change at low-T disappears because the SSE of YIG/Pt won't change sigh at low-T.By offering a mean of manipulating the interface,we have proven the contribution of interface to SSE.