Lattice distortion associated change in x-ray absorption linear dichroism and anisotropy of resistivity across thermal hysteresis region in the single crystal SrFeO3-δ
S. H. Hsieh (謝尚憲)1*, R. S. Solanki1, Y. F. Wang (王玉富)1, Y. C. Shao (邵禹成)1, S. H. Lee (李書翰)1, C. H. Yao (姚昌宏)1, C. H. Du (杜昭宏)1, H. T. Wang (王孝祖)2, J. W. Chiou (邱昭文)3, Y. Y. Chin (秦伊瑩)4, C. W. Pao (包志文)4, J. L. Chen (陳政龍)4, H. M. Tsai (蔡煌銘)4, J. F. Lee (李志甫)4, H. J. Lin (林宏基)4, W. F. Pong (彭維鋒)1
1Department of Physics, Tamkang University, New Taipei City, Taiwan
2Department of Physics, National Tsinghua University, Hsinchu, Taiwan
3Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan
4National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:Shang-Hsien Hsieh,
Local atomic and electronic properties of the high quality single crystal of SrFeO3-δ (δ ~ 0.14) have been studied using temperature-dependent x-ray absorption near-edge spectroscopy (XANES), x-ray linear dichroism (XLD), and extended x-ray absorption fine structure (EXAFS) at the Fe L3,2- and K-edge to investigate the origin of anisotropy in the resistivity along c-axis and ab-plane around the thermal hysteresis region (Neel temperature, TN~78 K). All the experiments have been carried out in the heating up and cooling down process. The results of Fe L3,2-edge XLD illustrate that in cooling down process from room temperature to below the transition temperature, the preferential occupancy of Fe majority-spin eg orbitals is 3d3z2-r2, however, it changes to 3dx2-y2 in heating up process during thermal hysteresis and restore to 3d3z2-r2 after thermal hysteresis. Local atomic structure analysis of temperature dependent Fe K-edge EXAFS data reveal the unusually large Debye-Waller factors around Fe atoms below TN. Further, the Fe-O bond lengths and Debye-Waller factors display anisotropic behavior as well as thermal hysteresis along ab-plane and c-axis around transition temperature. The anisotropic Fe-O bond lengths resulted in the stabilization of the Fe 3dx2-y2 or 3d3z2-r2 orbitals and gives rise to a different XLD during heating up and cooling down process and indeed responsible for the anisotropy of resistivity along ab-plane and c-axis in the thermal hysteresis region in SrFeO2.86.

Keywords: single crystal SrFeO3-δ, thermal hysteresis, x-ray linear dichroism (XLD), extended x-ray absorption fine structure (EXAFS), x-ray absorption near-edge spectroscopy (XANES)