Orbital Degree of Freedom and Phase Separation in Ferromagnetic Manganites at Finite Temperatures

TL;DR

This paper explores how orbital degrees of freedom influence phase separation in ferromagnetic manganites at finite temperatures, revealing the competition between superexchange and double exchange interactions and their role in charge segregation.

Contribution

It provides a detailed analysis of the orbital and spin phase diagram considering temperature and doping, highlighting the role of orbital anisotropy in phase separation.

Findings

Phase separation occurs over a wide temperature and doping range.

Orbital anisotropy causes discontinuous orbital state changes.

Charge segregation patterns relate to phase separation phenomena.

Abstract

The spin and orbital phase diagram for perovskite manganites are investigated as a function of temperature and hole concentration. The superexchange and double exchange interactions dominate the ferromagnetic phases in the low and high concentration regions of doped holes, respectively.The two interactions favor different orbital states each other. Between the phases, two interactions compete with each other and the phase separation appears in the wide range of temperature and hole concentration. The anisotropy of the orbital space causes discontinuous changes of the orbital state and promotes the phase separation. The relation between the phase separation and the stripe- and sheet-type charge segregation is discussed.