Spin dynamics in bulk MnNiGa and Mn1.4Pt0.9Pd0.1Sn investigated by muon spin relaxation [dataset]

We report muon spin relaxation and magnetometry studies of bulk Mn1.4Pt0.9Pd0.1Sn and MnNiGa, two materials which have recently been proposed to host topological magnetic states in thin lamella (antiskyrmions for Mn1.4Pt0.9Pd0.1Sn and biskyrmions for MnNiGa), and show spin reorientation transitions in bulk. These measurements shed light on the magnetic dynamics surounding the two magnetic phase transitions in each material. In particular, we demonstrate that the behaviour approaching the higher temperature transition in both samples is best understood by considering a slow decrease in the frequency of dynamics with temperature, rather than the sharp critical slowing down typical of second order transitions. Furthermore, at low temperatures the two samples both show spin dynamics over a broad range of frequencies that persist below the spin reorienation transition. The dynamic behavior we identify gives new insight into the bulk magnetism of these materials that may help underpin the stabilization of the topologically non-trivial phases that are seen in thin lamellae.

本工作报道了块体Mn₁.₄Pt₀.₉Pd₀.₁Sn与MnNiGa的μ子自旋弛豫（muon spin relaxation）及磁测量（magnetometry）研究。这两种材料近期被提出可在薄层中承载拓扑磁态：Mn₁.₄Pt₀.₉Pd₀.₁Sn对应反斯格明子（antiskyrmions），MnNiGa对应双斯格明子（biskyrmions），且二者在块体状态下均存在自旋重取向转变（spin reorientation transition）。上述实验结果阐明了两种材料各自的两类磁相变周围的磁动力学行为。尤为关键的是，本研究表明，对于两种样品在高温侧的相变行为，结合“动力学频率随温度缓慢降低”的模型进行阐释，要比二级相变（second order transition）典型的尖锐临界慢化（critical slowing down）模型更为合理。此外，在低温区域，两种样品在自旋重取向转变温度以下仍展现出宽频率范围的自旋动力学行为。本研究揭示的动力学行为，为理解这两种材料的块体磁性提供了新视角，或可为阐明薄层中观测到的非平庸拓扑相（topologically non-trivial phase）的稳定机制提供理论支撑。