The lattice parameters and the crystal and magnetic structures of Fe2SiO4 have been determined from 10 K to 1453 K by high-resolution time-of-flight neutron powder diffraction. Fe2SiO4 undergoes two antiferromagnetic phase transformations on cooling from room temperature: the first, at 65.4 K, is to a collinear antiferromagnet with moments on two symmetry-independent Fe ions; the second transition, at ~23 K, is to a structure in which the moments on one of the sets of Fe ions (those on the ‘M1 site’) become canted. The magnetic unit cell is identical to the crystallographic (chemical) unit cell and the space group remains Pbnm throughout. The magnetic structures have been refined and the results found to be in good agreement with previous studies; however, we have determined the spontaneous magnetostrictive strains, which have not been reported previously. In the paramagnetic phase of Fe2SiO4, at temperatures of 70 K and above, we find that the temperature dependence of the linear thermal expansion coefficient of the b axis takes an unusual form. In contrast to the behaviour of the expansion coefficients of the unit-cell volume and of the a and c axes, which show the expected reduction in magnitude below ~300 K, that of the b axis remains almost constant between ~70 K and 1000 K.

通过高分辨率飞行时间中子粉末衍射测定了10 K 至1453 K 范围内Fe 2 SiO 4的晶格参数以及晶体和磁性结构。 Fe 2 SiO 4从室温冷却时经历两次反铁磁相变：第一个是在 65.4 K 时，变为共线反铁磁体，其矩位于两个对称性无关的 Fe 离子上；第二个转变发生在约 23 K 时，其中一组 Fe 离子（“M1 位点”上的那些）上的力矩变为倾斜的结构。磁性晶胞与晶体（化学）晶胞相同，空间群始终保持Pbnm 。磁结构得到了细化，结果与之前的研究非常吻合；然而，我们已经确定了自发磁致伸缩应变，这是以前从未报道过的。在Fe 2 SiO 4顺磁相中，在70 K及以上的温度下，我们发现b轴线性热膨胀系数的温度依赖性呈现出一种不寻常的形式。与晶胞体积以及a轴和c轴的膨胀系数的行为相反，该行为显示了低于 ~300 K 时幅度的预期减小，b轴的膨胀系数在 ~70 K 和 1000 K 之间几乎保持恒定。