Spin Hall magnetoresistance and the effect of post-annealing temperature in the MOD-grown HoIG

Abstract

We present the fabrication of ultrathin Ho3Fe5O12 (HoIG) films on 111- oriented-Gd3Ga5O12 (GGG) via the metal-organic decomposition (MOD) method followed by a sequence annealing process. We characterized the crystal structure, surface morphology, and magnetic properties to study the effect of annealing temperature on the quality of MOD-grown HoIG films. For temperatures higher than 800 ⁰C, we observe the infiltration of Iron (Fe) from the HoIG film into the GGG substrate. In particular, the Fe-diffusion is significantly enhanced for a 1000 ⁰C-annealed sample of which crystal structure and magnetic properties are also affected. For temperatures lower than 800 ⁰C, on the other hand, the smooth surface and strong crystallinity cannot be guaranteed. This suggests that an annealing temperature of 800 ⁰C is the optimal condition for the MOD-grown HoIG film. The quality of the sample is further confirmed by measuring the spin Hall magnetoresistance (SMR) of HoIG/Pt, in which we found the unconventional angular dependence and comparable spin mixing conductance similar to the previous reports in other single crystalline IGs.