Anomalous Nernst effect in a microfabricated thermoelectric element made of chiral antiferromagnet Mn3Sn
Anomalous Nernst effect in a microfabricated thermoelectric element made of chiral antiferromagnet Mn3Sn
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DOI：
10.1063/1.5000815
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发表时间：
2017-11
影响因子：
4
通讯作者：
H. Narita;M. Ikhlas;M. Kimata;A. Nugroho;S. Nakatsuji;Y. Otani
中科院分区：
文献类型：
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作者：
H. Narita;M. Ikhlas;M. Kimata;A. Nugroho;S. Nakatsuji;Y. Otani
为了实现手性反铁磁体Mn3Sn型热电堆，采用聚焦离子束(FIB)光刻技术制备了由Ta/Al2O3/Mn3Sn层状结构组成的热电元件。在该器件中，Ta层起到加热器的作用，产生焦耳热量通过Al_2O_3绝缘层扩散到薄的Mn3Sn层。测量的能斯特信号在300K的温度梯度和磁场中表现出明显的滞后，其大小与Ta加热器电流的平方成正比。器件中的自发零场电压信号为几个μV量级，与体相单晶Mn3Sn体在温度梯度下观察到的电压信号几乎相同的数量级。利用有限元模拟的温度梯度确定了微细加工单元的反常能斯特系数SANE。得到的SANE值为0.27μV/K，与文献报道的块体单晶Mn3SnSANE的实验值(0.3μV/K)一致。这一结果表明，FIB微细加工不会显著改变块体Mn3Sn体的热电性能。由于手性反铁磁体几乎不产生杂散场，因此我们的研究为通过密集堆积微细制作的反铁磁体元件来制备高效热电堆开辟了道路。
Toward realizing a thermopile made of the chiral anti-ferromagnet Mn3Sn, focused ion beam (FIB) lithography was employed to microfabricate a thermoelectric element consisting of a Ta/Al2O3/Mn3Sn layered structure. In this device, the Ta layer acts as a heater producing Joule heat diffusing across the Al2O3 insulating layer into the thin Mn3Sn layer. The measured Nernst signal exhibits a clear hysteresis in an applied temperature gradient and magnetic field at 300 K, and its magnitude is proportional to the square of the electrical current applied to the Ta heater. The spontaneous, zero field voltage signal in the device is of the order of a few μV, which is almost the same order of magnitude as observed in the bulk single-crystal Mn3Sn under a temperature gradient. The anomalous Nernst coefficient SANE of the microfabricated element was determined using a temperature gradient simulated by finite-element modeling. The obtained value of SANE is 0.27 μV/K, which is in good agreement with that of the reported experimental value of SANE (0.3 μV/K) for bulk single-crystal Mn3Sn. This result indicates that FIB microfabrication does not significantly alter the thermoelectric properties of bulk Mn3Sn. As the chiral antiferromagnet produces almost no stray field, our study opens the avenue for the fabrication of an efficient thermopile by densely packing the microfabricated antiferromagnetic elements.