Temperature-dependent phonon spectra of magnetic random solid solutions (磁性随机固溶体的温度依赖性声子谱)
Yuji Ikeda, Fritz Körmann, Biswanath Dutta, Abel Carreras, Atsuto Seko, Jörg Neugebauer & Isao Tanaka
npj Computational Materials 4:7 (2018)
doi:10.1038/s41524-018-0063-1
Published online:28 February 2018
Abstract| Full Text | PDF OPEN
摘要:本研究基于第一原理开发了一种计算工具,用于热磁波动等方面的磁随机固溶体声子模拟。该方法考虑了由磁激发和由化学紊乱引起的力常数波动。这一方法可准确地预测Fe-Pd和Fe-Pt Invar两种合金中,能观察到的横向声学模式随温度升高而出现的异常声子硬化。这种在传统谐波图像中无法解释的奇特行为,竟然是热磁波动的结果。本方法有可能直接用来对多种材料的物理行为提出新的解释,也可用来计算设计目前尚没有的全新材料。
Abstract:A first-principles-based computational tool for simulating phonons of magnetic random solid solutions including thermal magnetic fluctuations is developed. The method takes fluctuations of force constants due to magnetic excitations as well as due to chemical disorder into account.The developed approach correctly predicts the experimentally observed unusual phonon hardening of a transverse acoustic mode in Fe–Pdan Fe–Pt Invar alloys with increasing temperature.This peculiar behavior, which cannot be explained within a conventional harmonic picture, turns out to be a consequence of thermal magnetic fluctuations. The proposed methodology can be straightforwardly applied to a wide range of materials to reveal new insights into physical behaviors and to design materials through computation, which were not accessible so far.
Editorial Summary
Magnetic materials: Turning up the heat on disordered magnets (磁性材料:调节无序磁体的热量)
该研究开发了一种数值方法,可用来预测零上温区的无序磁性固体的原子振动。有精确的计算方法方可计算材料在不同温度下的振动模式,才能基于第一原理确定材料的热力学性质。然而,原子不均匀分布和量子磁性行为二者对合金造成的影响,都需要用特殊方法处理才能计算。来自日本、德国和荷兰的Yuji Ikeda及其同事,将有序磁系统方法与已有无序材料近似方法结合起来,设计了一种新方法。该方法成功地捕捉了Invar合金的非凡热膨胀性能,原子和磁性波动相互作用对这种性能有强烈影响。他们的方法也可能为高熵合金等复杂材料的物理现象提供新的解释。
Researchers have developed a numerical method to predict the atomic vibrations of disordered magnetic solids above zero temperature. Accurate methods for computing the vibrational modes of materials at different temperatures are needed to determine thermodynamic properties from first principles.However, for magnetic alloys the effects of the non-uniform distribution of atoms and quantum magnetic behaviour each require special techniques for calculations to be tractable. Yuji Ikeda and colleagues from Japan, Germany and the Netherlands have designed a scheme that combines an approach for ordered magnetic systems with established approximations for disordered materials.Their method successfully captures the unusual thermal expansion properties of Invar alloys, which are strongly affected by the interplay of atomic and magnetic fluctuations, and should provide insights into the physics of other complex materials such as high entropy alloys.