Influence of the cooperative Jahn-Teller effect on the transport- and magnetic properties of La_{7/8}Sr_{1/8}MnO_3 single crystals

TL;DR

This study investigates how the cooperative Jahn-Teller effect influences the transport and magnetic properties of La_{7/8}Sr_{1/8}MnO_3, revealing the interplay between orbital order, magnetic fields, and phase transitions.

Contribution

It provides new insights into the impact of orbital ordering and magnetic fields on the structural and magnetic phase transitions in low-doped manganite crystals.

Findings

Orbital ordering causes resistivity doubling at 269 K.

Magnetic fields lower the orbital ordering transition temperature.

High magnetic fields suppress magnetization anomalies associated with phase transitions.

Abstract

The low-doped magnetic perovskite La_{7/8}Sr_{1/8}MnO_3 undergoes within the paramagnetic-semiconducting phase a first-order structural transition due to antiferrodistorsive ordering of Jahn-Teller deformed MnO_6 octahedra. This allows to study not only the influence of the spin configuration on the magneto-transport properties (CMR effect) but also the role of orbital order and disorder. The orbital ordering transition (at 269 K in zero magnetic field) causes a doubling of the resistivity (regardless of the CMR effect in applied magnetic fields) and a drop of the paramagnetic susceptibility. The latter might be interpreted in terms of a shrinking of spin polarons. External magnetic fields shift the ordering transition to lower temperatures according to the field-induced decrease of the carrier localization. The magnetic field - temperature phase boundary line was investigated by means of magnetoresistance (up to 12 T) and pulsed-fields magnetization measurements up to 50 T. The pronounced magnetization anomalies, associated with the phase transition, vanish for fields exceeding 20 T. This behaviour has been attributed to a field-induced crossover from antiferrodistorsive order to a nondistorsive/ferromagnetic orbital configuration.