钙钛矿锰氧化物的磁相变临界行为及磁热效应研究进展  

Research progress of critical behaviors and magnetocaloric effects of perovskite manganites

作　　者：张鹏 朴红光 张英德[3] 黄焦宏[3] Zhang Peng;Piao Hong-Guang;Zhang Ying-De;Huang Jiao-Hong(School of Science,Hubei University of Technology,Wuhan 430068,China;Research Institute for Magnetoelectronics&Weak Magnetic-field Detection,College of Science,China Three Gorges University,Yichang 443002,China;Baotou Research Institute of Rare Earths,Baotou 014030,China)

机构地区：[1]湖北工业大学理学院,武汉430068 [2]三峡大学理学院,磁电子与纳磁探测研究所,宜昌443002 [3]包头稀土研究院,包头014030

出　　处：《物理学报》2021年第15期25-40,共16页Acta Physica Sinica

基　　金：湖北省自然科学基金(批准号:ZRMS2018001866);湖北工业大学博士启动金(批准号:BSQD13030);国家重点研发计划(批准号:2017YFB0903702)资助的课题.

摘　　要：钙钛矿锰氧化物具备磁热效应高、性能稳定可控、成本低廉等显著优点,是适用于室温磁制冷领域的优质候选工质材料之一.但该体系内部电磁学性质复杂,特别是关于铁磁相互作用机制和磁相变性质等关键科学问题仍然有待深入探索.分析磁相变临界行为有利于揭示磁性材料内部的铁磁相互作用距离和机制等重要信息.本文简要介绍了钙钛矿锰氧化物相关理论背景以及各种磁相变临界行为分析方法,随后归纳了近年来多种钙钛矿锰氧化物的磁相变临界行为研究,系统对比了不同带宽典型锰氧化物在单晶和多晶形态下的磁相变临界行为,讨论了A/B位掺杂不同元素以及不同制备工艺条件对其临界参数的影响,对其中渡越于一级和二级相变的La-Ca-Mn-O体系在不同磁场范围下的临界参数演化进行了讨论.最后对处于磁相变三重临界点附近的部分锰氧化物材料的磁热效应研究进行了总结和展望.Hole-doped perovskite-type manganites have received intensive attention due to their intriguing physical phenomena such as giant magnetocaloric effect and magnetic-phase transitions.However,the mechanism of internal ferromagnetic interaction still needs to be further explored due to the complex natures of competing double-exchange(DE)and super-exchange(SE)interaction,Jahn-Teller(JT)polaron localization,charge ordering,and phase separation scenarios.Critical exponent analysis near magnetic phase transition is a powerful tool to investigate the details of the ferromagnetic interactions and has been used frequently in various magnetocaloric materials.In this article,the critical behavior analyses of perovskite manganites in recent years are comprehensively reviewed.A large number of studies have shown that even in single-phase materials with uniform structure and composition,the critical behavior can be affected by multiple factors such as grain boundary density and the degree of disorder,making them difficult to fully describe the intrinsic ferromagnetism.In this review,firstly,the critical behaviors of typical manganites with different bandwidths in single crystal and polycrystalline are discussed.In a double-exchange dominated system such as La-Sr-Mn-O,short-range 3D-Heisenberg model is basically in good accordance with optimally-doped single crystal sample.However,it would be replaced by long-range mean-field critical behavior in polycrystalline sample when the correlation length exceeds the crystallite size.In a typical intermediate bandwidth system such as La-Ca-Mn-O exhibiting a complex phase diagram described by competing SE/DE interactions,JT polaron localization/delocalization,and Griffith phase disorder,the critical exponent can vary from 3D-Heisenberg model to tricritical mean-field model,for the crossover from first to second order phase transition.Secondly,the studies of elements doping and different fabrication methods indicate that the critical behavior of manganites can be effectively modulated,and

关 键 词：钙钛矿锰氧化物 磁相变临界行为 磁热效应 

分 类 号：TB34[一般工业技术—材料科学与工程] O469[理学—凝聚态物理]