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Structural phase transition in Tb 5 (Si 0.6 Ge 0.4 ) 4 at low temperature
Author(s) -
Kupsch A.,
Levin A. A.,
Meyer D. C.
Publication year - 2005
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200410306
Subject(s) - monoclinic crystal system , crystallography , orthorhombic crystal system , phase transition , magnetic refrigeration , bond length , phase (matter) , materials science , crystal structure , ferromagnetism , paramagnetism , chemistry , condensed matter physics , magnetization , physics , organic chemistry , quantum mechanics , magnetic field
Herein we report on crystallographic details of a structural phase transition measured with powdered Tb 5 (Si 0.6 Ge 0.4 ) 4 at low temperatures (150 and 130 K). The pseudo‐binary compound is monoclinic at room temperature ( P 112 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 Gd 5 Si 2 Ge 2 , that is a shear movement of pairs of nearly rigid slabs of atoms along a direction by 0.84 Å and the tremendous increase of selected (Si/Ge)‐(Si/Ge) distances from 2.64 to 3.59 Å in between those slabs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)