Magnetic Field Melting of the Charge-Ordered State of La0.5Ca0.5MnO3: A Local Structure Perspective

TL;DR

This study investigates how magnetic fields influence the local structure and magnetic phases of La0.5Ca0.5MnO3, revealing phase transitions and structural reordering associated with melting of charge order.

Contribution

It provides a detailed local structural perspective on magnetic field-induced phase transitions in La0.5Ca0.5MnO3, highlighting the correlation between structure and magnetic phases.

Findings

Identification of three distinct structural regions under magnetic fields.

Observation of Gaussian Mn-O distribution at high fields indicating ferromagnetic dominance.

Correlation between structural reordering and resistivity changes.

Abstract

The local structure about the Mn site in the half doped system La0.5Ca0.5MnO3 was measured in magnetic fields up 10 T to probe the melting of the charge ordered state. Examination of the Mn-O and Mn-Mn correlations reveal three distinct regions in the structure-field diagram. A broad region with weak field dependence (mainly antiferromatnetic phase below 7.5 T), a narrow-mixed phase region near ~ 8.5 T followed by a ferromagnetic phase region with strong field-structure coupling. At high field the Mn-O radial distribution becomes Gaussian and the Mn-Mn correlations are enhanced - consistent with the dominance of a ferromagnetic phase. The exponential change in resistivity in the first region (observed in transport measurements) is dominated by the reordering of the moments on the Mn sites from CE type antiferromagnetic to ferromagnetic order with only a weak change in the local distortions of the MnO6 octahedra.