钴氧化物中晶格与自旋的关联耦合效应研究  

Strong spin-lattice entanglement in cobaltites

作　　者：陈盛如 林珊 洪海涛 崔婷 金桥 王灿[1,2,4] 金奎娟 郭尔佳[1,2] Chen Sheng-Ru;Lin Shan;Hong Hai-Tao;Cui Ting;Jin Qiao;Wang Can;Jin Kui-Juan;Guo Er-Jia(Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences&Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China;Materials Science and Technology Division,Oak Ridge National Laboratory,Oak Ridge,TN 37831,USA;Songshan Lake Materials Laboratory,Dongguan 523808,China)

机构地区：[1]中国科学院物理研究所,北京凝聚态物质科学国家研究中心,北京100190 [2]中国科学院大学物理科学学院和材料与光电研究中心,北京100049 [3]橡树岭国家实验室,材料科学与技术分部,橡树岭37831 [4]松山湖材料实验室,东莞523808

出　　处：《物理学报》2023年第9期33-50,共18页Acta Physica Sinica

基　　金：国家重点研发计划青年项目(批准号:2020YFA0309100);国家重点研发计划(批准号:2019YFA0308500);国家自然科学基金联合重点项目(批准号:U22A20263);国家自然科学基金原创探索计划(批准号:52250308);国家自然科学基金(批准号:11974390);国家自然科学基金创新研究群体项目(批准号:11721404);中国科学院依托大科学装置开展建制化科研项目;中国科学院先导B类项目(批准号:XDB33030200);粤港澳中子散射科学技术联合实验室项目(批准号:HT-CSNS-DG-CD-0080/2021)资助的课题。

摘　　要：强关联电子体系具有多序参量耦合且极易受到外场高效调控的特性.钴氧化物(LaCoO3)是一类典型的多铁性(兼具铁弹性和铁磁性)氧化物材料,受到了研究者们广泛和深入的研究.过去,针对钴氧化物的研究都集中于应力作用下的铁弹性相变和结构调控方面.近年来,研究人员新奇地发现钴氧化物薄膜在张应力作用下发生顺磁到铁磁相转变,但其根源一直存在较大争议.部分实验证据表明应力将会导致钴离子价态降低产生自旋态转变,而另一些研究者认为应力诱导的纳米畴结构会呈现高自旋态的长程有序排列,才是钴氧化物薄膜铁磁性的主要原因.本综述主要介绍近几年来钴氧化物薄膜和异质结中自旋与晶格之间关联耦合效应的系列进展.在保持钴离子价态不变时,通过薄膜厚度、晶格失配应力、晶体对称性、表面形貌、界面氧离子配位和氧八面体倾转等结构因素诱导钴氧化物薄膜的自旋态可逆转变,从而形成高度可调的宏观磁性.进而,研究者们利用原子级精度可控的薄膜生长技术构筑了单原胞层钴氧化物超晶格,通过高效的结构调控,实现了超薄二维磁性氧化物材料.这些系列进展不仅澄清了强关联电子体系中晶格与自旋等序参量之间的强耦合关系,而且为实现氧化物自旋电子器件所需的超薄室温铁磁材料提供了优良的候选者.Strongly correlated electronic system contains strong coupling among multi-order parameters and is easy to efficiently tune by external field.Cobaltite(LaCoO3)is a typical multiferroic(ferroelastic and ferromagnetic)material,which has been extensively investigated over decades.Conventional research on cobaltites has focused on the ferroelastic phase transition and structure modulation under stress.Recently,researchers have discovered that cobaltite thin films undergo a paramagnetic-to-ferromagnetic phase transition under tensile strain,however,its origin has been controversial over decades.Some experimental evidence shows that stress leads the valence state of cobalt ions to decrease,and thus producing spin state transition.Other researchers believe that the stress-induced nano-domain structure will present a long-range ordered arrangement of high spin states,which is the main reason for producing the ferromagnetism of cobalt oxide films.In this paper,we review a series of recent researches of the strong correlation between spin and lattice degrees of freedom in cobalt oxide thin films and heterojunctions.The reversible spin state transition in cobalt oxide film is induced by structural factors such as thin-film thickness,lattice mismatch stress,crystal symmetry,surface morphology,interfacial oxygen ion coordination,and oxygen octahedral tilting while the valence state of cobalt ions is kept unchanged,and thus forming highly adjustable macroscopic magnetism.Furthermore,the atomic-level precision controllable film growth technology is utilized to construct single cell layer cobaltite superlattices,thereby achieving ultrathin two-dimensional magnetic oxide materials through efficient structure regulation.These advances not only clarified the strong coupling between lattice and spin order parameters in the strongly correlated electronic system,but also provided excellent candidate for the realization of ultra-thin room temperature ferromagnets that are required by oxide spintronic devices.

关 键 词：铁磁氧化物 晶格畸变 极化中子反射 自旋态转变 铁弹相变 

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]