We use a symmetry-motivated approach to analyse neutron pair distribution function data to investigate the mechanism of negative thermal expansion (NTE) in ReO$_3$. This analysis shows that the local structure of ReO$_3$ is dominated by an in-phase octahedral tilting mode and that the octahedral units are far less flexible to scissoring type deformations than the octahedra in the related compound ScF$_3$. These results support the idea that structural flexibility is an important factor in NTE materials, allowing the phonon modes that drive a volume contraction of the lattice to occupy a greater volume in reciprocal space. The lack of flexibility in ReO$_3$ restricts the NTE-driving phonons to a smaller region of reciprocal space, limiting the magnitude and temperature range of NTE. In addition, we investigate the thermal expansion properties of the material at high temperature and do not find the reported second NTE region. Finally, we show that the local fluctuations, even at elevated temperatures, respect the symmetry and order parameter direction of the observed $P4/mbm$ high pressure phase of ReO$_3$. The result indicates that the motions associated with rigid unit modes are highly anisotropic in these systems.
Origin of the spin reorientation transitions in (Fe$_{1-x}$Co$_{x}$)$_{2}$B alloys
报道了（Fe $_{1-x}$ Co $_{x}$）$_{2}$ B合金磁晶各向异性能$K$的低温测量结果，并利用第一性原理电子结构分析阐明了这种各向异性的起源.计算的浓度依赖性$K(x)$的最大值附近的$x=0.3$和$x=0.8$附近的最小值与实验非常一致。这种依赖性可追溯到自旋轨道选择规则和填充的电子带增加电子浓度。在最佳Co浓度下，$K$强烈依赖于四方性，并且在$c/a$比率适度增加3%下加倍，这表明可以使用外延或化学应变进一步增强磁晶各向异性。
Decoupled domain-texture switching from magnetic easy axis in kagome ferromagnet EuTi3Bi4
Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Renmin University of China（中国人民大学）；Fudan University（复旦大学）
Lattice dynamics effects on the magnetocrystalline anisotropy energy: application to MnBi
采用基于超软赝势和密度泛函微扰理论的第一性原理完全相对论方案，研究了铁磁二元化合物MnBi的磁晶各向异性自由能.我们发现，由于不同的磁化方向（面内和垂直于平面）的声子色散的差异给出了高温和低温相的振动自由能之间的差异。这种对磁晶各向异性能（MAE）常数$K_u$的振动贡献是不可忽略的。当通过PBESol交换和相关泛函计算对MAE的能量贡献时，声子贡献的添加允许得到与实验合理一致的$T = 0$ K $K_u$和自旋重取向转变温度。
Observation of Magnetic-Anisotropy Crossover and High-Temperature Skyrmions in the Dirac Magnet Fe3Ge with a Distorted Kagome Lattice
Zhejiang University of Technology（浙江工业大学）；Fudan University（复旦大学）；Nanjing University of Posts and Telecommunications（南京邮电大学）；Ningbo University（宁波大学）；Academia Sinica（中央研究院）；Shanghai University（上海大学）；Suzhou University of Technology（苏州科技大学）；Qufu Normal University（曲阜师范大学）；National Taiwan Normal University（台湾师范大学）；Zhejiang University（浙江大学）；Shanghai Jiao Tong University（上海交通大学）
Temperature-dependent magnetocrystalline anisotropy of rare earth/transition metal permanent magnets from first principles: The light RCo$_5$ (R=Y, La-Gd) intermetallics
The origin of anisotropy and high density of states in the electronic structure of Cr$_2$GeC by means of polarized soft X-ray spectroscopy and ab initio calculations
