# Anisotropy in the thermal hysteresis of resistivity and charge density wave nature of single crystal SrFeO3-delta: X-ray absorption and photoemission studies

## TL;DR

This study investigates the anisotropic resistivity and charge density wave behavior in SrFeO3-{delta} single crystals using temperature-dependent x-ray absorption and photoemission spectroscopy, revealing orbital and structural changes across thermal hysteresis.

## Contribution

It provides new insights into the orbital and structural origins of anisotropic resistivity and charge density wave phenomena in SrFeO3-{delta} through combined spectroscopic and structural analysis.

## Key findings

- Persistent out-of-plane orbitals during cooling
- In-plane orbitals during warming below Tm
- Band gap opening at low temperature indicating charge density wave

## Abstract

The local electronic and atomic structures of the high-quality single crystal of SrFeO3-{delta} ({delta}~0.19) were studied using temperature-dependent x-ray absorption and valence-band photoemission spectroscopy (VB-PES) to investigate the origin of anisotropic resistivity in the ab-plane and along the c-axis close to the region of thermal hysteresis (near temperature for susceptibility maximum, Tm~78 K). All experiments herein were conducted during warming and cooling processes. The Fe L3,2-edge X-ray linear dichrois results show that during cooling from room temperature to below the transition temperature, the unoccupied Fe 3d eg states remain in persistently out-of-plane 3d3z2-r2 orbitals. In contrast, in the warming process below the transition temperature, they change from 3d3z2-r2 to in-plane 3dx2-y2 orbitals. The nearest-neighbor (NN) Fe-O bond lengths also exhibit anisotropic behavior in the ab-plane and along the c-axis below Tm. The anisotropic NN Fe-O bond lengths and Debye-Waller factors stabilize the in-plane Fe 3dx2-y2 and out-of-plane 3d3z2-r2 orbitals during warming and cooling, respectively. Additionally, a VB-PES study further confirms that a relative band gap opens at low temperature in both the ab-plane and along the c-axis, providing the clear evidence of the charge-density-wave nature of SrFeO3-{delta} ({delta}~ 0.19) single crystal.

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Source: https://tomesphere.com/paper/1703.00646