Electrical properties of single crystal Yttrium Iron Garnet ultra-thin films at high temperatures

摘要

We report a study on the electrical properties of 19 nm thick Yttrium IronGarnet (YIG) films grown by liquid phase epitaxy. The electrical conductivityand Hall coefficient are measured in the high temperature range [300,400]~Kusing a Van der Pauw four-point probe technique. We find that the electricalresistivity decreases exponentially with increasing temperature following anactivated behavior corresponding to a band-gap of $E_g\approx 2$ eV, indicatingthat epitaxial YIG ultra-thin films behave as large gap semiconductor, and notas electrical insulator. The resistivity drops to about $5\times 10^3$~$\Omega\cdot \text{cm}$ at $T=400$ K. We also infer the Hall mobility, which is foundto be positive ($p$-type) at 5 cm$^2$/(V$\cdot$sec) and about independent oftemperature. We discuss the consequence for non-local transport experimentsperformed on YIG at room temperature. These electrical properties areresponsible for an offset voltage (independent of the in-plane field direction)whose amplitude, odd in current, grows exponentially with current due to Jouleheating. These electrical properties also induce a sensitivity to theperpendicular component of the magnetic field through the Hall effect. In ourlateral device, a thermoelectric offset voltage is produced by a temperaturegradient along the wire direction proportional to the perpendicular componentof the magnetic field (Righi-Leduc effects).