Ali Anzar, Sharma G, Vardhan Abhinay, Pasrija Kanika, Rajput S, Maitra T, Kumar Sanjeev, Singh Yogesh
Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO 140306, India.
J Phys Condens Matter. 2019 Jul 31;31(30):305803. doi: 10.1088/1361-648X/ab151a. Epub 2019 Apr 1.
We present a combined experimental and theoretical study to understand the magnetism and magnetocaloric behavior of the double perovskite NdNiMnO. The magnetic susceptibility data confirms a ferromagnetic transition with [Formula: see text] K. An additional feature at T = 25 K, indicative of antiferromagnetic correlations, is present. A positive magnetocaloric effect (MCE) near [Formula: see text] and a negative MCE around T = 25 K is inferred from the temperature dependence of the change in magnetic entropy at low magnetic fields. The negative MCE peak is suppressed on the application of a magnetic field and can be made to switch to a conventional positive MCE upon increasing magnetic field. We understand and reproduce these features in Monte Carlo simulations of a phenomenological Heisenberg model for NdNiMnO. The validity of the model is tested using density functional theory calculations. We argue that this simple understanding of the experimental observations in terms of two antiferromagnetically coupled sublattices allows these results to be useful across a broader class of magnetocaloric materials.
我们开展了一项结合实验与理论的研究，以了解双钙钛矿NdNiMnO的磁性和磁热行为。磁化率数据证实了在[公式：见原文]K时发生铁磁转变。在T = 25 K处存在一个额外特征，表明存在反铁磁关联。从低磁场下磁熵变化的温度依赖性推断，在[公式：见原文]附近存在正磁热效应（MCE），在T = 25 K左右存在负磁热效应。负磁热效应峰值在施加磁场时受到抑制，并且在增加磁场时可转变为传统的正磁热效应。我们在NdNiMnO的唯象海森堡模型的蒙特卡罗模拟中理解并重现了这些特征。使用密度泛函理论计算对该模型的有效性进行了测试。我们认为，基于两个反铁磁耦合亚晶格对实验观测结果的这种简单理解，使得这些结果在更广泛的磁热材料类别中具有实用性。
