Unveiling New Magnetic Phases of Undoped and Doped Manganites

TL;DR

This study reveals new magnetic phases in undoped and doped manganites using theoretical models, showing potential for large magneto-resistance effects even without doping.

Contribution

It introduces the E-type AFM phase in undoped manganites and the ${ m C_x E_{1-x}}$-type phase in doped manganites, expanding understanding of their magnetic ground states.

Findings

Discovery of the E-type AFM phase in undoped manganites.

Identification of the ${ m C_x E_{1-x}}$-type AFM phase in doped manganites.

Potential for large magneto-resistance effects in undoped Mn oxides.

Abstract

Novel ground-state spin structures in undoped and lightly-doped manganites are here investigated based on the orbital-degenerate double-exchange model, by using mean-field and numerical techniques. In undoped manganites, a new antiferromagnetic (AFM) state, called the E-type phase, is found adjacent in parameter space to the A-type AFM phase. Its structure is in agreement with recent experimental results. This insulating E-AFM state is also competing with a ferromagnetic metallic phase as well, suggesting that large magneto-resistant effects could exist even in undoped Mn oxides. For doped layered manganites, the phase diagram includes another new AFM phase of the ${\rm C_x E_{1-x}}$-type. Experimental signatures of the new phases are discussed.