Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal.
Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal.
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DOI：
10.1038/s41566-017-0086-z
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发表时间：
2018-03
期刊：
影响因子：
35
通讯作者：
Nakatsuji S
中科院分区：
文献类型：
--
作者：
Higo T;Man H;Gopman DB;Wu L;Koretsune T;van 't Erve OMJ;Kabanov YP;Rees D;Li Y;Suzuki MT;Patankar S;Ikhlas M;Chien CL;Arita R;Shull RD;Orenstein J;Nakatsuji S
当偏振光束入射到磁性材料的表面上时，反射光经历偏振旋转。这种磁光克尔效应（MOKE）已经在各种铁磁和亚铁磁材料中得到了深入的研究，因为它为电子和磁性以及包括磁光记录在内的各种应用提供了强大的探针。近年来，反铁磁体（AFM）作为高密度和超快存储器件的自旋电子材料受到了广泛的关注，这是由于它们的杂散磁场非常小，并且与铁磁材料相比，自旋动力学速度快了几个数量级。事实上，MOKE已被证明是有用的反铁磁（AF）状态的研究和应用。虽然限于绝缘体，但已知某些类型的AFM表现出大的MOKE，因为它们是弱铁磁体，这是由于共线自旋结构的倾斜。在这里，我们报告了在室温下AF金属中首次观察到的大MOKE信号。特别是，我们发现，尽管M ~0.002 µB/Mn的磁化强度非常小，但非共线AF金属Mn 3Sn表现出大的零场MOKE，极克尔旋转角为20毫度，与铁磁金属相当。我们的第一性原理计算已经澄清，在非共线的Néel状态的磁性八极铁电有序可能会导致一个大的MOKE，即使在其完全补偿AF状态没有自旋磁化。这种大的MOKE进一步允许成像的磁八极域和它们的磁场引起的反转。AF金属中大MOKE的观察将为使用AFM研究磁畴动力学以及自旋电子学开辟新的途径。
When a polarized light beam is incident upon the surface of a magnetic material, the reflected light undergoes a polarization rotation. This magneto-optical Kerr effect (MOKE) has been intensively studied in a variety of ferro- and ferrimagnetic materials because it provides a powerful probe for electronic and magnetic properties as well as for various applications including magneto-optical recording. Recently, there has been a surge of interest in antiferromagnets (AFMs) as prospective spintronic materials for high-density and ultrafast memory devices, owing to their vanishingly small stray field and orders of magnitude faster spin dynamics compared to their ferromagnetic counterparts. In fact, the MOKE has proven useful for the study and application of the antiferromagnetic (AF) state. Although limited to insulators, certain types of AFMs are known to exhibit a large MOKE, as they are weak ferromagnets due to canting of the otherwise collinear spin structure. Here we report the first observation of a large MOKE signal in an AF metal at room temperature. In particular, we find that despite a vanishingly small magnetization of M ~0.002 µB/Mn, the non-collinear AF metal Mn3Sn exhibits a large zero-field MOKE with a polar Kerr rotation angle of 20 milli-degrees, comparable to ferromagnetic metals. Our first-principles calculations have clarified that ferroic ordering of magnetic octupoles in the non-collinear Néel state may cause a large MOKE even in its fully compensated AF state without spin magnetization. This large MOKE further allows imaging of the magnetic octupole domains and their reversal induced by magnetic field. The observation of a large MOKE in an AF metal should open new avenues for the study of domain dynamics as well as spintronics using AFMs.
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