Evidence for a short-range chemical order of Ge atoms and its critical role in inducing a giant magnetocaloric effect in Gd5Si1.5Ge2.5

被引：6
作者：
Kou, Ronghui [1 ]
Gao, Jianrong [1 ]
Nie, Zhihua [2 ]
Wang, Yandong [3 ]
Brown, Dennis E. [4 ]
Ren, Yang [5 ]
机构：
[1] Northeastern Univ, Key Lab Electromagnet Proc Mat, Minist Educ, Shenyang 110819, Liaoning, Peoples R China
[2] Beijing Inst Technol, Coll Mat Sci & Engn, Beijing 100124, Peoples R China
[3] Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing 100083, Peoples R China
[4] Northern Illinois Univ, Dept Phys, De Kalb, IL 60115 USA
[5] Argonne Natl Lab, Adv Photon Source, Argonne, IL 60439 USA
来源：
JOURNAL OF ALLOYS AND COMPOUNDS | 2019年 / 808卷
基金：
中国国家自然科学基金;
关键词：
Rare earth compound; Crystal structure; Magnetocaloric effect; Synchrotron radiation; X-ray diffraction; MAGNETIC REFRIGERATION; ELECTRONIC-STRUCTURE; CRYSTAL-STRUCTURE; GD-5(SIXGE1-X)(4); TRANSITION; SYSTEM;
D O I：
10.1016/j.jallcom.2019.151751
中图分类号：
O64 [物理化学（理论化学）、化学物理学];
学科分类号：
070304 ; 081704 ;
摘要：
Crystal structure and magnetic properties of Gd5Si1.5Ge2.5 and Gd4.9Zr0.1Si1.5Ge2.5 were investigated using high-energy X-ray diffraction and magnetic measurements. Results showed that a Zr substitution for 2% Gd reduces unit cell volumes of a room-temperature monoclinic and a low-temperature orthorhombic lattice and a difference between them at a magnetostructural transition. At a microscopic level, the Zr substitution increases length of disconnected interlayer T-T bonds of the monoclinic lattice at the expense of length of connected interlayer T-bonds (T =Si, Ge). These opposing changes of the interlayer TeT bonds provided evidence for existence of a short-range chemical order of Ge atoms in lattices of Gd5Si1.5Ge2.5 and its weakening by the Zr substitution. Magnetic measurements revealed that the Zr substitution brings about a change of the magnetic structure and a reduction of a giant magnetocaloric effect of Gd5Si1.5Ge2.5. Based on such structural and magnetic changes due to the Zr substitution, we propose a relation between the short-range chemical order and the total entropy change at the magnetostructural transition. Using this relation, a giant magnetocaloric effect and an annealing effect observed over a wide range of Gd-5(Si,Ge)(4) composition can be explained quantitatively. (C) 2019 Elsevier B.V. All rights reserved.
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页数：11
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