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首页> 外文期刊>Crystal Research and Technology: Journal of Experimental and Industrial Crystallography >Structural phase transition in Tb-5(Si0.6Ge0.4)(4) at low temperature
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Structural phase transition in Tb-5(Si0.6Ge0.4)(4) at low temperature

机译：Tb-5（Si0.6Ge0.4）（4）的低温结构相变

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摘要

Herein we report on crystallographic details of a structural phase transition measured with powdered Tb-5(Si0.6Ge0.4)4 at low temperatures (150 and 130 K). The pseudo-binary compound is monoclinic at room temperature (P112(1)/a). Changes of reflection intensities and positions in the diffraction patterns indicate a structural phase transition between 100 K and 150 K, where the compound orders in an orthorhombic structure (Pnma). This is in accordance with a magnetic phase transition from paramagnetic to ferromagnetic state (T-C = 150 K), where the compound exhibits the giant magnetocaloric effect. Split-up crystallographic sites of the monoclinic unit cell degenerate to sites of higher symmetry in the orthorhombic structure. Changes in the corresponding bond lengths are listed in detail. It turned out that both phases coexist at the selected temperatures but the phase content changes significantly. The observed phase transition is very similar to that reported for Gd5Si2Ge2, that is a shear movement of pairs of nearly rigid slabs of atoms along a direction by 0.84 Angstrom and the tremendous increase of selected (Si/Ge)-(Si/Ge) distances from 2.64 to 3.59 Angstrom in between those slabs.
机译：本文中，我们报告了在低温（150和130 K）下用粉末Tb-5（Si0.6Ge0.4）4测量的结构相变的晶体学细节。伪二元化合物在室温下为单斜晶（P112（1）/ a）。反射强度和衍射图样位置的变化表明结构相变在100 K和150 K之间，其中化合物以正交晶体结构（Pnma）有序排列。这与从顺磁态到铁磁态（T-C = 150 K）的磁性相变一致，其中该化合物表现出巨大的磁热效应。单斜晶胞的分裂晶体学位点退化为斜方晶结构中对称性更高的位点。详细列出了相应键长的变化。结果表明，两种相在选定的温度下共存，但是相含量却发生了显着变化。观察到的相变与Gd5Si2Ge2所报告的相变非常相似，即成对的近乎刚性的原子对沿0.84埃方向的剪切运动，并且选定的（Si / Ge）-（Si / Ge）距离大大增加在这些平板之间介于2.64至3.59埃之间。

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