Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature
Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature
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DOI：
10.1038/nature15723
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发表时间：
2015-11-12
期刊：
影响因子：
64.8
通讯作者：
Higo, Tomoya
中科院分区：
文献类型：
--
作者：
Nakatsuji, Satoru;Kiyohara, Naoki;Higo, Tomoya
在铁磁导体中，电流可以在零外加磁场中感应出横向电压降：这种反常的霍尔效应（1）被观察到与磁化强度成正比，因此在零磁场中的反铁磁体中通常看不到（2）。理论和实验的最新发展为使用Berry相位概念理解反常霍尔效应提供了一个框架，并且这一观点导致预测，在某些条件下，在没有净自旋磁化的自旋液体和反铁磁体中可能出现大的反常霍尔效应（4-8）。虽然这种自发的霍尔效应现在已经在自旋液体状态下观察到（9），但迄今为止还没有关于反铁磁体的零场异常霍尔效应的报道。在这里，我们报告一个大的反常霍尔效应的反铁磁体，具有消失小磁化的经验证据。特别是，我们发现Mn 3Sn，一种具有非共线120度自旋序的反铁磁体（10，11），在室温下表现出约20每欧姆每厘米的大的反常霍尔电导率，在低温下超过100每欧姆每厘米，达到与铁磁金属相同的数量级（3）。值得注意的是，手征反铁磁态具有非常弱的软铁磁矩，大约为每个Mn原子0.002个玻尔磁子（参考文献10，12），这使得我们可以用大约几百奥斯特的小磁场来切换霍尔效应的符号。这种大的反常霍尔效应的软响应对于包括自旋电子学在内的各种应用都是有用的，例如，开发一种几乎不产生扰动杂散场的存储器件。
In ferromagnetic conductors, an electric current may induce a transverse voltage drop in zero applied magnetic field: this anomalous Hall effect(1) is observed to be proportional to magnetization, and thus is not usually seen in antiferromagnets in zero field(2). Recent developments in theory and experiment have provided a framework for understanding the anomalous Hall effect using Berry-phase concepts', and this perspective has led to predictions that, under certain conditions, a large anomalous Hall effect may appear in spin liquids and antiferromagnets without net spin magnetization(4-8). Although such a spontaneous Hall effect has now been observed in a spin liquid state(9), a zero-field anomalous Hall effect has hitherto not been reported for antiferromagnets. Here we report empirical evidence for a large anomalous Hall effect in an antiferromagnet that has vanishingly small magnetization. In particular, we find that Mn3Sn, an antiferromagnet that has a non-collinear 120-degree spin order(10,11), exhibits a large anomalous Hall conductivity of around 20 per ohm per centimetre at room temperature and more than 100 per ohm per centimetre at low temperatures, reaching the same order of magnitude as in ferromagnetic metals(3). Notably, the chiral antiferromagnetic state has a very weak and soft ferromagnetic moment of about 0.002 Bohr magnetons per Mn atom (refs 10, 12), allowing us to switch the sign of the Hall effect with a small magnetic field of around a few hundred oersted. This soft response of the large anomalous Hall effect could be useful for various applications including spintronics for example, to develop a memory device that produces almost no perturbing stray fields.