Chiral Magnetism and High-Temperature Skyrmions in B20-Ordered Co-Si
Chiral Magnetism and High-Temperature Skyrmions in B20-Ordered Co-Si
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DOI：
10.1103/physrevlett.124.057201
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发表时间：
2020-02-06
影响因子：
8.6
通讯作者：
Sellmyer, David J.
中科院分区：
文献类型：
--
作者：
Balasubramanian, Balamurugan;Manchanda, Priyanka;Sellmyer, David J.
具有手性晶体结构和螺旋自旋结构的磁体作为潜在的自旋电子材料最近引起了人们的广泛关注，但其相对较低的磁有序温度是一个缺点。虽然钴长期以来被认为是促进高温磁有序的元素，但大多数富钴合金是非手性的，并且表现出共线磁序而不是螺旋磁序。从晶体学角度来看，B20 有序化合物 CoSi 由于其手性结构而属于例外，但它不表现出任何类型的磁序。在这里，我们使用非平衡处理来生产 B20 有序 Co1+xSi1-x，最大 Co 溶解度为 x = 0.043。高于临界过量 Co 含量 (x(c) = 0.028）时，合金呈磁有序，当 x = 0.043 时，获得临界温度 T-c = 328 K，这是所有 B20 型磁体中最高的。该合金的晶体结构支持由 Dzyaloshinskii-Moriya 相互作用引起的自旋螺旋，根据磁性测量，我们估计螺旋的周期性约为 17 nm。我们的密度泛函计算解释了高磁序温度和短周期性的结合，即量子相变，其中过量的钴自旋通过主基质耦合。
Magnets with chiral crystal structures and helical spin structures have recently attracted much attention as potential spin-electronics materials, but their relatively low magnetic-ordering temperatures are a disadvantage. While cobalt has long been recognized as an element that promotes high-temperature magnetic ordering, most Co-rich alloys are achiral and exhibit collinear rather than helimagnetic order. Crystallographically, the B20-ordered compound CoSi is an exception due to its chiral structure, but it does not exhibit any kind of magnetic order. Here, we use nonequilibrium processing to produce B20-ordered Co1+xSi1-x, with a maximum Co solubility of x = 0.043. Above a critical excess-Co content (x(c) = 0.028), the alloys are magnetically ordered, and for x = 0.043, a critical temperature T-c = 328 K is obtained, the highest among all B20-type magnets. The crystal structure of the alloy supports spin spirals caused by Dzyaloshinskii-Moriya interactions, and from magnetic measurements we estimate that the spirals have a periodicity of about 17 nm. Our density-functional calculations explain the combination of high magnetic-ordering temperature and short periodicity in terms of a quantum phase transition where excess-cobalt spins arc coupled through the host matrix.