Electrical properties of epitaxial yttrium iron garnet ultrathin films at high temperatures
Electrical properties of epitaxial yttrium iron garnet ultrathin films at high temperatures
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DOI：
10.1103/physrevb.97.064422
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发表时间：
2017-09
影响因子：
3.7
通讯作者：
N. Thiéry;V. Naletov;L. Vila;A. Marty;A. Brenac;J. Jacquot;G. D. Loubens;M. Viret;A. Anane;V. Cros;J. Youssef;V. Demidov;S. Demokritov;O. Klein
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文献类型：
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作者：
N. Thiéry;V. Naletov;L. Vila;A. Marty;A. Brenac;J. Jacquot;G. D. Loubens;M. Viret;A. Anane;V. Cros;J. Youssef;V. Demidov;S. Demokritov;O. Klein
研究了液相外延生长的19 nm厚的YIG薄膜的电学性质。用范德堡四探针法测量了在[300,400]~K高温范围内的电导率和霍尔系数。我们发现，YIG薄膜的电阻率随温度的升高呈指数下降，其激活行为对应于禁带宽度约为2 eV，表明外延YIG超薄膜的行为是大禁带半导体，而不是电绝缘体。在T=400$K时，其电阻率降至约5美元，约为10^3$~(Omega\CDOT\Text{cm})的5倍。我们还推测了霍尔迁移率在5 cm×2$/(V$\CDOT$sec)处为正($p$型)，且与温度无关。我们讨论了在YIG上进行的室温非局域输运实验的结果。这些电学特性导致偏置电压(与面内场方向无关)，其幅度奇数电流由于焦耳加热而随电流呈指数增长。这些电学性质还通过霍尔效应引起对磁场垂直分量的敏感。在我们的横向器件中，沿导线方向的温度梯度与磁场的垂直分量成正比(Righi-Leduc效应)，从而产生热电偏置电压。
We report a study on the electrical properties of 19 nm thick Yttrium Iron Garnet (YIG) films grown by liquid phase epitaxy. The electrical conductivity and Hall coefficient are measured in the high temperature range [300,400]~K using a Van der Pauw four-point probe technique. We find that the electrical resistivity decreases exponentially with increasing temperature following an activated behavior corresponding to a band-gap of $E_g\approx 2$ eV, indicating that epitaxial YIG ultra-thin films behave as large gap semiconductor, and not as 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 found to be positive ($p$-type) at 5 cm$^2$/(V$\cdot$sec) and about independent of temperature. We discuss the consequence for non-local transport experiments performed on YIG at room temperature. These electrical properties are responsible for an offset voltage (independent of the in-plane field direction) whose amplitude, odd in current, grows exponentially with current due to Joule heating. These electrical properties also induce a sensitivity to the perpendicular component of the magnetic field through the Hall effect. In our lateral device, a thermoelectric offset voltage is produced by a temperature gradient along the wire direction proportional to the perpendicular component of the magnetic field (Righi-Leduc effects).