Spin State Disproportionation in Insulating Ferromagnetic LaCoO3 Epitaxial Thin Films

Chen, Shanquan1; Chang, Jhong-Yi2; Zhang, Qinghua3; Li, Qiuyue4,5; Lin, Ting3; Meng, Fanqi3; Huang, Haoliang6; Si, Yangyang1; Zeng, Shengwei7; Yin, Xinmao8; Duong, My Ngoc2; Lu, Yalin6; Chen, Lang9; Guo, Er-Jia3; Chen, Hanghui5,10; Chang, Chun-Fu11; Kuo, Chang-Yang2,12; Chen, Zuhuang1,13

2023-07-01

10.1002/advs.202303630

ADVANCED SCIENCE   影响因子和分区

2198-3844

The origin of insulating ferromagnetism in epitaxial LaCoO3 films under tensile strain remains elusive despite extensive research efforts are devoted. Surprisingly, the spin state of its Co ions, the main parameter of its ferromagnetism, is still to be determined. Here, the spin state in epitaxial LaCoO3 thin films is systematically investigated to clarify the mechanism of strain-induced ferromagnetism using element-specific X-ray absorption spectroscopy and dichroism. Combining with the configuration interaction cluster calculations, it is unambiguously demonstrated that Co3+ in LaCoO3 films under compressive strain (on LaAlO3 substrate) is practically a low-spin state, whereas Co3+ in LaCoO3 films under tensile strain (on SrTiO3 substrate) have mixed high-spin and low-spin states with a ratio close to 1:3. From the identification of this spin state ratio, it is inferred that the dark strips observed by high-resolution scanning transmission electron microscopy indicate the position of Co3+ high-spin state, i.e., an observation of a spin state disproportionation in tensile-strained LaCoO3 films. This consequently explains the nature of ferromagnetism in LaCoO3 films. The study highlights the importance of spin state degrees of freedom, along with thin-film strain engineering, in creating new physical properties that do not exist in bulk materials.

epitaxial strain insulating ferromagnetism lacoo(3) thin films spin state disproportionation X-ray absorption spectroscopy

SCI ; EI

英语

其他

the Fundamental Research Funds for the Central Universities[2020B1515020029] ; Talent Recruitment Project of Guangdong[JCYJ20200109112829287] ; Ministry of Science and Technology in Taiwan[KQTD20200820113045083] ; Max Planck-POSTECH-Hsinchu Center for Complex Phase Materials[HIT.OCEF.2022038] ; National Natural Science Foundation of China[2019QN01C202] ; Beijing Natural Science Foundation[MOST 110-2112-M-A49-002-MY3] ; null[52072400] ; null[52025025] ; null[Z190010] ; null[2021YFE0107900]

Chemistry ; Science & Technology - Other Topics ; Materials Science

Chemistry, Multidisciplinary ; Nanoscience & Nanotechnology ; Materials Science, Multidisciplinary

WOS:001033751300001

WILEY

20233014440111

Aluminum compounds ; Circular dichroism spectroscopy ; Cobalt compounds ; Degrees of freedom (mechanics) ; Dichroism ; Ferromagnetism ; High resolution transmission electron microscopy ; Insulation ; Lanthanum compounds ; Scanning electron microscopy ; Strontium titanates ; Tensile strain ; Titanium compounds ; X ray absorption spectroscopy

Insulating Materials:413 ; Magnetism: Basic Concepts and Phenomena:701.2 ; Magnetic Materials:708.4 ; Light/Optics:741.1 ; Optical Devices and Systems:741.3 ; Chemical Products Generally:804 ; Mechanics:931.1 ; Atomic and Molecular Physics:931.3

Web of Science

1.Harbin Inst Technol, Sch Mat Sci & Engn, Shenzhen 518055, Peoples R China
2.Natl Yang Ming Chiao Tung Univ, Dept Electrophys, Hsinchu 30010, Taiwan
3.Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China
4.East China Normal Univ, Dept Elect Sci, Shanghai 200241, Peoples R China
5.NYU Shanghai, NYU ECNU Inst Phys, Shanghai 200124, Peoples R China
6.Univ Sci & Technol China, Hefei Natl Res Ctr Phys Sci Microscale, Hefei 230026, Peoples R China
7.Natl Univ Singapore, Fac Sci, Dept Phys, Singapore 117551, Singapore
8.Shanghai Univ, Phys Dept, Shanghai Key Lab High Temp Supercond, Shanghai 200444, Peoples R China
9.Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China
10.NYU, Dept Phys, New York, NY 10012 USA
11.Max Planck Inst Chem Phys Solids, Nothnitzer Str 40, D-01187 Dresden, Germany
12.Natl Synchrotron Radiat Res Ctr, 101 Hsin Ann Rd, Hsinchu 30076, Taiwan
13.Harbin Inst Technol, Flexible Printed Elect Technol Ctr, Shenzhen 518055, Peoples R China

Chen, Shanquan,Chang, Jhong-Yi,Zhang, Qinghua,et al. Spin State Disproportionation in Insulating Ferromagnetic LaCoO3 Epitaxial Thin Films[J]. ADVANCED SCIENCE,2023,10(27).

Chen, Shanquan.,Chang, Jhong-Yi.,Zhang, Qinghua.,Li, Qiuyue.,Lin, Ting.,...&Chen, Zuhuang.(2023).Spin State Disproportionation in Insulating Ferromagnetic LaCoO3 Epitaxial Thin Films.ADVANCED SCIENCE,10(27).

Chen, Shanquan,et al."Spin State Disproportionation in Insulating Ferromagnetic LaCoO3 Epitaxial Thin Films".ADVANCED SCIENCE 10.27(2023).