Magnetic-Field-Independent Ultrasonic Dispersions in the Magnetically Robust Heavy Fermion System SmOs4Sb12
Tatsuya Yanagisawa, Hitoshi Saito, Hiroyuki Hidaka, Hiroshi Amitsuka, Koji Araki, Mitsuhiro Akatsu, Yuichi Nemoto, Terutaka Goto, Pei-Chun Ho, Ryan E. Baumbach, M. Brian Maple
Elastic properties of the filled skutterudite compound SmOs$_4$Sb$_{12}$ have been investigated by ultrasonic measurements. The elastic constant $C_{11}(ω)$ shows two ultrasonic dispersions at $\sim$15 K and $\sim$53 K for frequencies $ω$ between 33 and 316 MHz, which follow a Debye-type formula with Arrhenius-type temperature-dependent relaxation times, and remain unchanged even with applied magnetic fields up to 10 T. The corresponding activation energies were estimated to be $E_2$ = 105 K and $E_1$ = 409 K, respectively. The latter, $E_1$, is the highest value reported so far in the Sb-based filled skutterudites. The presence of magnetically robust ultrasonic dispersions in SmOs$_4$Sb$_{12}$ implies a possibility that an emergence of a magnetically insensitive heavy fermion state in this system is associated with a novel local charge degree of freedom which causes the ultrasonic dispersion.
Magnetic order and excitations in the magnetically intercalated van der Waals material Cr$_{\frac{1}{4}}$NbSe$_2$
The Institute for Solid State Physics, University of Tokyo（东京大学固体离子体研究所）；Department of Applied Physics, University of Tokyo（东京大学应用物理系）；Institute of Materials Structure Science, High Energy Accelerator Research Organization（高能加速器研究机构物质结构科学研究所）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）；College of Engineering, Shibaura Institute of Technology（芝浦工业大学工程学院）；Research Center for Advanced Science and Technology, University of Tokyo（东京大学先端科学技术研究中心）
Spin-wave directional anisotropies in antiferromagnetic Ba$_{3}$NbFe$_{3}$Si$_{2}$O$_{14}$
Ba $_{3}$ NbFe $_{3}$ Si $_{2}$ O $_{14}$（硅酸镧镓）在结构和磁性上是单畴手性的，通过竞争对称交换相互作用诱导磁螺旋。利用中子散射，我们证明了反铁磁硅酸镓中的自旋波具有方向各向异性。在沿$c$轴施加时间反演对称性破缺磁场时，当动量转移$\pm$ $\vec{Q}$或施加磁场$\pm$ $μ_{0}$ H的符号反转时，自旋波能量不同。当在结晶学$ab$ -平面内施加场时，自旋波色散是定向的\textit{isotropic}，并且在$\pm$ $μ_{0}$ H中是对称的。然而，在自旋波强度中观察到方向各向异性。我们讨论了这种方向性各向异性的分散在硅酸镓的动态单元格交错磁化的场致进动。方向各向异性，或通常被称为非互易响应，可以在没有Dzyaloshinskiii-Moriya相互作用或其他自旋轨道耦合效应的情况下发生在反铁磁相中。
