Negative thermal expansion in (Sc,Ti)Fe2 induced by an unconventional magnetovolume effect†,Materials Horizons

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Negative thermal expansion in (Sc,Ti)Fe2 induced by an unconventional magnetovolume effect†
Materials Horizons ( IF 12.2 ) Pub Date : 2019-09-17 , DOI: 10.1039/c9mh01025d
Yuzhu Song _{1,

2,

3,

4} , Qiang Sun _{4,

5,

6,

7,

8} , Meng Xu _{1,

2,

3,

4} , Ji Zhang _{4,

9,

10,

11,

12} , Yiqing Hao _{4,

13,

14,

15} , Yongqiang Qiao _{1,

2,

3,

4} , Shantao Zhang _{4,

9,

10,

11,

12} , Qingzhen Huang _{16,

17,

18} , Xianran Xing _{1,

2,

3,

4} , Jun Chen _{1,

2,

3,

4}

Affiliation

Beijing Advanced Innovation Center for Materials Genome Engineering, and School of Mathematics and Physics
University of Science and Technology Beijing
Beijing 100083
China
International Laboratory for Quantum Functional Materials of Henan
School of Physics and Engineering
Zhengzhou University
Zhengzhou 450001
National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering
College of Engineering and Applied Science & Collaborative Innovation Center of Advanced Microstructures
Nanjing University
Nanjing 210093
State Key Laboratory of Surface Physics and Department of Physics
Fudan University
Shanghai 200433
NIST Center for Neutron Research, National Institute of Standards and Technology
Gaithersburg
USA

Negative thermal expansion (NTE) has been found in some magnetic functional materials due to the magnetovolume effect (MVE), in which an order-to-disorder magnetic transition occurs. Here, we report an unconventional MVE which can induce the crossover from the common positive thermal expansion of the end members of ScFe₂ and TiFe₂ to the NTE in the solid solution of (Sc_1−xTi_x)Fe₂ (x = 0.6, α_V = −28.36 × 10⁻⁶ K⁻¹, 125–205 K). The direct evidence of neutron powder diffraction and first-principles calculations discloses that the decrease of intrinsic magnetic moments at the Fe(2a) site results in the ferromagnetic transition from one to another, which causes a stronger negative contribution to thermal expansion than the conventional MVE. The pair distribution function analysis verifies that the decrease in the nearest distance of Fe(6h)–Fe(6h) lying in the ab plane results in the shrinkage of the a(b) axis. The analysis of anisotropic atomic displacement parameters excludes the phonon induced NTE mechanism. Furthermore, an intriguing zero thermal expansion has been found in Sc_0.55Ti_0.45Fe₂ (10–250 K). The present study provides an approach to achieve NTE or controllable thermal expansion, which may be used to enhance other magnetic-related effects, such as the magnetocaloric and barocaloric effect.

中文翻译：

（Sc，Ti）Fe _2的负热膨胀是由非常规的磁烟流效应引起的†

由于磁粒效应（MVE），在某些磁性功能材料中发现了负热膨胀（NTE），其中发生了有序到无序的磁跃迁。在这里，我们报告了一种非常规的MVE，它可以引起（Sc _1-_x Ti _x）Fe ₂（x = 0.6 ）固溶中ScFe ₂和TiFe ₂的端部成员从共同的正热膨胀过渡到NTE。，α _V = -28.36×10 ^-6 ķ ^-1，125–205 K）。中子粉末衍射和第一性原理计算的直接证据表明，Fe（2a）位置处固有磁矩的减少导致铁磁从一个跃迁到另一个，从而比常规MVE对热膨胀产生更大的负贡献。对分布函数分析验证，位于ab平面中的Fe（6h）–Fe（6h）最近距离的减小会导致a（b）轴收缩。各向异性原子位移参数的分析排除了声子引起的NTE机理。此外，在Sc _0.55 Ti _0.45 Fe _2中发现了令人着迷的零热膨胀（10–250 K）。本研究提供了一种实现NTE或可控制的热膨胀的方法，该方法可用于增强其他与磁有关的效应，例如磁热效应和压热效应。

更新日期：2020-01-04

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