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

JOURNAL OF ALLOYS AND COMPOUNDS

卷:808

Article

Kou, Ronghui¹  Gao, Jianrong¹  Nie, Zhihua²  Wang, Yandong³  Brown, Dennis E.⁴  Ren, Yang⁵ 

[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

关键词: Rare earth compound;    Crystal structure;    Magnetocaloric effect;    Synchrotron radiation;    X-ray diffraction;   

DOI  :  10.1016/j.jallcom.2019.151751

来源: Elsevier

【 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.

【 授权许可】

Free