We report on the magnetic properties of the manganite Bi_{1-x}Ca_{x}MnO_3 (x=0.33) at low temperature. The analysis of the field expansion of the ac susceptibility and the observation of aging properties make clear that a spin glass phase appears below T = 39K, in the presence of magnetic order. Neutron scattering shows both magnetic Bragg scattering and magnetic diffusion at small angles, and confirms this coexistence. In contrast to Pr_{1-x}Ca_{x}MnO_3 (x=0.3-0.33) which exhibits a mesoscopic phase separation responsible for a field driven percolation, the glassy and short range ferromagnetic order observed here does not cause colossal magnetoresistance (CMR).
Linking Thermal History to Shear Band Interaction and Macroscopic Ductility in Metallic Glasses
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences（中国科学院宁波材料技术与工程研究所）；Institute of Advanced Magnetic Materials, College of Materials & Environmental Engineering, Hangzhou Dianzi University（杭州电子科技大学材料与环境工程学院先进磁性材料研究所）；State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所非线性力学国家重点实验室）；School of Engineering Science, University of Chinese Academy of Sciences（中国科学院大学工程科学学院）；Beijing Computational Science Research Center（北京计算科学研究中心）
Nature and distribution of iron sites in a sodium silicate glass investigated by neutron diffraction and EPSR simulation
采用高分辨中子衍射和经验势结构精细化（EPSR）方法研究了NaFeSi 2 O 6（NFS）玻璃的短程和中程结构。大部分（~60%）的Fe是4-配位的（[4]Fe），仅对应于三价铁，Fe 3+，距离d[4] Fe 3 +-O=1.87 $\pm$ 0.01 π。这与通过玻璃化学计量预测的3D结构不同。大多数[4] Fe 3+位点的存在说明了与晶体NaFeSi 2 O 6的结构不同的玻璃结构，晶体NaFeSi 2 O 6仅含有八面体Fe 3+。玻璃结构的EPSR模拟表明，[4] Fe 3+随机分布在硅酸盐网络中，与硅酸盐四面体共角。大多数[4] Fe 3+位置的存在不同于相应晶相的结构，其仅包含八面体Fe 3+。[4] Fe 3+的网络形成行为，加上Na+离子作为电荷补偿剂的存在，是含铁玻璃的特殊物理性质的起源，例如随着铁浓度的增加，硅酸钠玻璃的弹性模量增加。我们的数据还提供了5配位Fe的直接证据，平均距离d[5]Fe-O=2.01 $\pm$ 0.01 Å。该第二Fe群体涉及Fe 2+和Fe 3+两者。5-配位的Fe原子倾向于通过主要共享边缘而分离。三价铁在NFS玻璃中的双重作用的直接结构证据为理解NFS玻璃的特殊性质提供了支持，例如磁性，光学，电子或热力学性质。
In this study we have reported the borate-based glasses in the form of $4(75 - x)B-2O-3 - xBi_2O_3 - 10Na_2O - 10CaO - 5Al_2O_3$ ($0 \le x \le 25$ mol%) for gamma-ray and neutron shielding applications, and for this purpose mass attenuation coefficients of these glasses have been investigated using Geant4 code and XCOM program in the energy range between 1 keV and 10 MeV. A good agreement between the simulation results and computed values was observed. The obtained values were then used to calculate the other related shielding parameters such as half value layer (HVL), mean free path (MFP) and…
Comprehensive Research Organization for Science and Society (CROSS)（综合科学研究组织）；Tohoku University（东北大学）；Japan Atomic Energy Agency (JAEA)（日本原子能研究开发机构）；Ibaraki University（茨城大学）；Tokyo City University（东京都立大学）；The University of Tokyo（东京大学）
Using the notion of eigenstrain produced by the defects formed in a material exposed to high energy neutron irradiation, we develop a method for computing macroscopic elastic stress and strain arising in components of a fusion power plant during operation. In a microstructurally isotropic material, the primary cause of macroscopic elastic stress and strain fields is the spatial variation of neutron exposure. We show that under traction-free boundary conditions, the volume-average elastic stress always vanishes, signifying the formation of a spatially heterogeneous stress state, combining compr…
Glassy magnetic phase driven by short range charge and magnetic ordering in nanocrystalline La$_{1/3}$Sr$_{2/3}$FeO$_{3-δ}$: Magnetization, Mossbauer, and polarised neutron studies
Tetragonal distorted spinel of CuMn2-xTixO4 (x = 0, 0.25 and 0.50) was prepared by solid state reaction method followed by neutron diffraction, FTIR spectroscopy, dielectric spectroscopy and magnetization measurements. The neutron diffraction and FTIR spectroscopy provide the information regarding phase formation. But, the magnetic susceptibility clearly shows the ferri-magnetic order below 76K associated with meta-magnetic state which turns to spin-glass behaviour upon Ti-substitution for Mn in CuMn2O4. In addition, the room temperature M(H) of all the spinels are described by the Arrott's pl…
Neutron and X-ray Diffraction Reveal the Limits of Long-Range Machine Learning Potentials for Medium-Range Order in Silica Glass
Department of Material Design and Innovation, University at Buffalo（材料设计与创新系，布法罗大学）；NVIDIA Corp.（NVIDIA公司）；X-ray Science Division, Advanced Photon Source, Argonne National Laboratory（先进光子源X射线科学部，阿贡国家实验室）
