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arXiv 1809.02567cond-mat.mtrl-sci
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微结构缺陷诱导的Dzyaloshinskiii-Moriya相互作用

Microstructural-defect-induced Dzyaloshinskii-Moriya interaction

Andreas Michels, Denis Mettus, Ivan Titov, Artem Malyeyev, Mathias Bersweiler, Philipp Bender, Inma Peral, Rainer Birringer, Yifan Quan, Patrick Hautle, Joachim… 展开作者

Andreas Michels, Denis Mettus, Ivan Titov, Artem Malyeyev, Mathias Bersweiler, Philipp Bender, Inma Peral, Rainer Birringer, Yifan Quan, Patrick Hautle, Joachim Kohlbrecher, Dirk Honecker, Jesus Rodriguez Fernandez, Luis Fernandez Barquin, Konstantin L. Metlov

摘要:

反对称的Dzyaloshinskiii-Moriya相互作用(Dzyaloshinskiii-Moriya interaction,简称Dzyaloshinskii-Moriya)对非中心对称晶体结构的磁性系统中Skyrmion织构的稳定和手性控制起着决定性的作用。一个较少研究的方面是,这种相互作用被认为是在晶体磁性材料的晶格缺陷附近,由于局部结构反转对称性破缺。如果这种情况导致了相当大的影响,这意味着手性引入到一个非常大的类别的磁性材料-缺陷丰富的系统,如多晶磁体。在这里,我们的实验表明,微结构缺陷引起的磁共振引起的极化依赖的非对称项的小角中子散射(SANS)截面的多晶铁磁体与中心对称的晶体结构。使用微磁学连续理论的理论预测支持的结果。Arrott在1963年已经证实了这种效应,并证明了纳米晶体铽和钬(具有大的晶界密度)以及机械变形的微晶钴(具有大的位错密度)。散射的不对称性的分析允许一个确定的缺陷引起的折射率常数,$D = 0.45 \pm 0.07 \, \mathrm{mJ/m^2}$的Tb在$100 \, \mathrm{K}$。我们的研究证明了一般的相关性的缺陷丰富的铁磁体的磁性微结构与消失的内禀磁性。极化SANS是决定性的揭示签名的缺陷引起的电子转移,这是有关的独特的依赖性的极化SANS截面上的手征相互作用。这一发现为研究无序材料中缺陷引起的skyrmionic磁化织构开辟了道路。

英文摘要:

The antisymmetric Dzyaloshinskii-Moriya interaction (DMI) plays a decisive role for the stabilization and control of chirality of skyrmion textures in various magnetic systems exhibiting a noncentrosymmetric crystal structure. A less studied aspect of the DMI is that this interaction is believed to be operative in the vicinity of lattice imperfections in crystalline magnetic materials, due to the local structural inversion symmetry breaking. If this scenario leads to an effect of sizable magnitude, it implies that the DMI introduces chirality into a very large class of magnetic materials---defect-rich systems such as polycrystalline magnets. Here, we show experimentally that the microstructural-defect-induced DMI gives rise to a polarization-dependent asymmetric term in the small-angle neutron scattering (SANS) cross section of polycrystalline ferromagnets with a centrosymmetric crystal structure. The results are supported by theoretical predictions using the continuum theory of micromagnetics. This effect, conjectured already by Arrott in 1963, is demonstrated for nanocrystalline terbium and holmium (with a large grain-boundary density), and for mechanically-deformed microcrystalline cobalt (with a large dislocation density). Analysis of the scattering asymmetry allows one to determine the defect-induced DMI constant, $D = 0.45 \pm 0.07 \, \mathrm{mJ/m^2}$ for Tb at $100 \, \mathrm{K}$. Our study proves the generic relevance of the DMI for the magnetic microstructure of defect-rich ferromagnets with vanishing intrinsic DMI. Polarized SANS is decisive for disclosing the signature of the defect-induced DMI, which is related to the unique dependence of the polarized SANS cross section on the chiral interactions. The findings open up the way to study defect-induced skyrmionic magnetization textures in disordered materials.

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