Symmetry breaking in single crystal SrTiO$_3$ plates: EPR manifestations

TL;DR

This study reveals that millimeter-scale SrTiO$_3$ plates exhibit a symmetry-lowering tetragonal phase above 105 K, as evidenced by EPR, with the effect influenced by sample orientation and surface quality.

Contribution

The paper demonstrates a novel symmetry-breaking phase in SrTiO$_3$ plates above 105 K, distinct from the known low-temperature phase, and discusses its dependence on sample conditions.

Findings

Bulk symmetry lowers from cubic to tetragonal above 105 K.

The effect is not caused by residual stress.

Surface quality and orientation influence the phenomenon.

Abstract

Electron paramagnetic resonance studies of the impurity Fe$^{3+}$ and Mn$^{4+}$ centers indicate that the symmetry of the crystal structure of millimeter-scale strontium titanate plates above 105 K lowers in the bulk from cubic to tetragonal, different from that of the conventional low-temperature antiferrodistortive phase. It is shown that the effect does not originate from the residual stress; its magnitude (observed tetragonal distortion) and particular manifestations depend on plate orientation, surface quality and the geometry of a sample. Peculiarities of the observed phenomenon are presented and possible scenario of its realization is discussed.