典型磁性材料价电子结构研究面临的机遇与挑战  

Opportunity and challenge for study of valence electron structure in typical magnetic materials

作　　者：唐贵德 李壮志[2] 马丽[2] 吴光恒[1] 胡凤霞[1] Tang Gui-De;Li Zhuang-Zhi;Ma Li;Wu Guang-Heng;Hu Feng-Xia(State Key Laboratory of Magnetism,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;Hebei Advanced Thin Film Laboratory,College of Physics and Information Engineering,Hebei Normal University,Shijiazhuang 050024,China)

机构地区：[1]中国科学院物理研究所,磁学国家重点实验室,北京100190 [2]河北师范大学物理学院,河北省新型薄膜材料实验室,石家庄050024

出　　处：《物理学报》2020年第2期35-45,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11174069);河北省自然科学基金(批准号:E2015205111)资助的课题~~

摘　　要：目前在磁性材料磁有序现象研究中广泛使用的交换作用、超交换作用和双交换作用模型形成于1950年代及其以前,这些模型都涉及材料中的价电子状态,但那时还没有充分的价电子状态实验依据.1970年代以来,有关价电子结构实验结果的报道越来越多,这些实验结果表明传统的磁有序模型需要改进.首先,大量电子谱实验表明,在氧化物中除存在负二价氧离子之外,还存在负一价氧离子,并且负一价氧离子的含量可达30%或更多.这说明以所有氧离子都是负二价离子为基本假设的超交换和双交换作用模型需要改进.其次,一些实验证明,铁、钴、镍自由原子的一部分4s电子在形成铁磁性金属的过程中变成了3d电子,这为探讨金属磁性与电输运性质的关系提供了依据.此外,即使在现代的密度泛函计算中,仍不能给出磁性交换作用能的函数表达式,只能采取各种不同模型进行模拟计算,从而使磁性材料的模拟计算遇到严重困难.寻求一个磁有序能的函数表达式可能是解决这个困难的途径.这些研究表明磁性材料价电子结构研究面临着重大的机遇与挑战.本文首先介绍一些典型的实验例证,然后介绍了基于这些实验结果的一套典型磁性材料的磁有序新模型,随后介绍了基于新模型的磁性材料价电子结构与旧模型的主要区别,最后指出了未来研究工作面临的挑战.The conventional magnetic ordering models,exchange interaction,super-exchange(SE)interaction and double exchange(DE)interaction models relating to the valence electron structure in the materials,were proposed about in or before the 1950’s,the time when there was little experimental evidence.Since the 1970’s,more and more experimental results for the valence electron states have been reported.These experimental results suggested that the conventional magnetic ordering models need improving.i)Many experimental results,including the electron energy-loss spectra(EELS),X-ray absorption spectra(XAS),and X-ray photoelectron spectra(XPS),indicate that there are O–anions in addition to O2–anions in oxides,and that the percentage of O–anions may reach 30%or more.This suggests that the SE model and DE model both need to improving,in which all oxygen anions are assumed to be O2–anions.ii)Several experimental results,including gamma radiation diffraction,XAS and magnetic circular dichroism spectra(XMCD),suggest that part of 4 s electrons enter into 3 d orbits and transit into the 3 d electrons in the process of forming metals from free atoms.The effect of the orbital magnetic moment on the magnetic moment of a bulk metal is far smaller than the spin magnetic moments.These provide the evidence of exploring the relation between magnetic moment and electrical resistivity of the magnetic metal.iii)Using density function theory(DFT)to fit physical properties yields plenty of results for many materials,but there exist serious difficulties for magnetic materials.This is due to magnetic ordering energy is included in the exchange correlation energy,which has been find no phenomenological expression so far,and has to be fitted using various models in DFT calculation.These investigations provide an opportunity to improve magnetic ordering models.Therefore,our group proposed three models of magnetic ordering in typical magnetic materials,they including an O 2 p itinerant electron model for magnetic oxides(IEO model),a new it

关 键 词：磁有序模型 磁性氧化物 磁性金属和合金 光电子谱 

分 类 号：TM27[一般工业技术—材料科学与工程]