Crystal and magnetic structures of the layer Compound TlMnF4

The crystal structure and the magnetic properties of the fluoromanganate(III) TlMnF₄ have been investigated. The structure has been refined down to R/wR of 0.057/0.043 in the monoclinic I2/a space group with the unit cell constants a = 539.7(2) pm; b = 544.1(2) pm; c = 1248.4(5) pm; β = 90.19(3)° (Z = 4). TlMnF₄ is characterized by a layer structure formed of MnF₆ octahedra sharing their four equatorial corners. Within each octahedron the Mn? F distances range from 178 pm to 215 pm. The intralayer magnetic interaction (J/K) has been evaluated to be approximately ?0.45 K by fitting the experimental susceptibility in the 10–300 K range using the quadratic layer Heisenberg model. A 3 D-antiferromagnetic ordering occurs at T_n = 4.2(5) K. The magnetic cell corresponding to the nuclear one but with a primitive symmetry. The magnetic structure has been refined down to R = 0.0528 in the P2′/a′ magnetic group. The Mn^III moments are colinear to the b-axis and show antiparallel ordering within the layers.     

ITER用内锡法Nb3Sn超导线材的不可逆温度研究

本文采用超导量子干涉仪(SQUID)测定了一种国际热核聚变实验堆(ITER)项目用内锡法Nb3Sn超导线材的不可逆温度,测量方法是在恒定磁场下循环温度,即将温度以一定间隔从10K上升到20K,然后再返回到10K,测定磁矩的偏离温度.所得结果可用于从生成最佳Nb-Sn相组成方面来优化A15相成相热处理制度.本研究得出的结论是,对于像ITER使用的高场磁体超导线来说,鉴于其需要在较高磁场下有高的临界电流密度,就需要将超导线的热处理温度适当提高一些.本实验所用Nb3Sn超导线材的最适宜热处理制度为675°C/128小时,这样可以得到最佳不可逆温度特性,即最佳的A15相组成.     

Neutron inelastic scattering study of exchange interactions in a ruthenium V dimer a3CaRu2O9

Inelastic neutron scattering measurements have been performed on the binuclear Ru(V) cluster compound Ba₃CaRu₂O₉. The S = 0 →S = 1 transition split levels of the electronic ground state has been observed. The value for the exchange parameter is very close to that obtained from magnetic susceptibility measurements. The observed intensity ratios of the neutron inelastic scattering transition agree well with those calculated from a simple spin-spin coupling model for the ruthenium pair.     

Magnetic characterisation of the ternary carbide ThFe11C x (1.5≤x≤2) by57Fe Mössbauer spectroscopy

A⁵⁷Fe Mössbauer spectroscopy analysis of the ternary carbide ThFe₁₁C _x withx=1.5 and 1.8 has permitted to clearly identify the three different Fe sublattices from their relative abundance. Moreover, direct bonds exist between carbon atoms and iron atoms of one of the three sublattices, yielding a relatively large decrease of the local magnetic moment. A spin reorientation phenomenon (SR), taking place at low temperature, is shown to be of first order type. Both the exchange interactions and magnetocrystalline anisotropy parameters are very sensitive to the carbon stoichiometry. They are analysed for their role on the shifts inT _c andT _SR respectively.