Bajaj Naini, Roy Aditya Prasad, Khandelwal Ashish, Chattopadhyay M K, Sathe Vasant, Mishra Sanjay K, Mittal Ranjan, Babu Peram Delli, Le Manh Duc, Niedziela Jennifer L, Bansal Dipanshu
Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, MH 400076, India.
Free Electron Laser Utilization Laboratory, Raja Ramanna Centre for Advanced Technology, Indore, MP 452013, India.
J Phys Condens Matter. 2021 Jan 18;33(12). doi: 10.1088/1361-648X/abd781.
Direct engineering of material properties through exploitation of spin, phonon, and charge-coupled degrees of freedom is an active area of development in materials science. However, the relative contribution of the competing orders to controlling the desired behavior is challenging to decipher. In particular, the independent role of phonons, magnons, and electrons, quasiparticle coupling, and relative contributions to the phase transition free energy largely remain unexplored, especially for magnetic phase transitions. Here, we study the lattice and magnetic dynamics of biferroic yttrium orthochromite using Raman, infrared, and inelastic neutron spectroscopy techniques, supporting our experimental results with first-principles lattice dynamics and spin-wave simulations across the antiferromagnetic transition at∼ 138 K. Spectroscopy data and simulations together with the heat capacity () measurements, allow us to quantify individual entropic contributions from phonons (0.01 ± 0.01atom), dilational (0.03 ± 0.01atom), and magnons (0.11 ± 0.01atom) across. High-resolution phonon measurements conducted in a magnetic field show that anomalous-dependence of phonon energies acrossoriginates from magnetoelastic coupling. Phonon scattering is primarily governed by the phonon-phonon coupling, with little contribution from magnon-phonon coupling, short-range spin correlations, or magnetostriction effects; a conclusion further supported by our thermal conductivity measurements conducted up to 14 T, and phenomenological modeling.
通过利用自旋、声子和电荷耦合自由度来直接设计材料特性是材料科学中一个活跃的发展领域。然而，竞争序对控制期望行为的相对贡献难以解读。特别是，声子、磁振子和电子的独立作用、准粒子耦合以及对相变自由能的相对贡献在很大程度上仍未得到探索，尤其是对于磁相变。在这里，我们使用拉曼光谱、红外光谱和非弹性中子光谱技术研究了双铁性正铬酸钇的晶格和磁动力学，并通过跨越约138K反铁磁转变的第一性原理晶格动力学和自旋波模拟来支持我们的实验结果。光谱数据和模拟结果以及热容测量，使我们能够量化在整个过程中来自声子（0.01±0.01原子）、膨胀（0.03±0.01原子）和磁振子（0.11±0.01原子）的个体熵贡献。在磁场中进行的高分辨率声子测量表明，声子能量在整个过程中的异常依赖性源于磁弹性耦合。声子散射主要由声子 - 声子耦合控制，磁振子 - 声子耦合、短程自旋相关性或磁致伸缩效应的贡献很小；我们在高达14T的热导率测量以及唯象模型进一步支持了这一结论。
