The magnetic structure of bixbyite a-Mn2O3: a combined density functional theory DFT+U and neutron diffraction study

Published

May 15, 2013

Author(s)

Eric J. Cockayne, Igor Levin, Hui Wu, Anna Liobet

Abstract

First principles density functional theory DFT+U calculations and experimental neutron diffraction structure refinements were used to determine the low-temperature crystallographic and magnetic structure of bixbyite a-Mn2O3. The energies of various magnetic arrangements, calculated from first principles, were fit to a cluster-expansion model using a Bayesian method that overcomes a problem of underfitting caused by the limited number of input magnetic configurations. The model was used to predict the lowest-energy magnetic states. Experimental determination of magnetic structure benefited from optimized sample synthesis, which produced crystallite sizes large enough to yield a clear splitting of peaks in the neutron powder diffraction patterns, thereby enabling magnetic-structure refinements under the correct orthorhombic symmetry. The refinements employed group theory to constrain magnetic models. Computational and experimental analyses independently converged to similar ground states, with identical antiferromagnetic ordering along a principal magnetic axis and secondary ordering along a single orthogonal axis, differing only by a phase factor in the modulation patterns. The lowest-energy magnetic states are compromise solutions to frustrated antiferromagnetic interactions between certain corner-sharing MnO6 octahedra.

Citation

Physical Review B

Volume

87

Pub Type

Journals

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DOI Link

Keywords

Mn2O3, bixbyite structure, antiferromagnetic ordering

Citation

Cockayne, E. , Levin, I. , Wu, H. and Liobet, A. (2013), The magnetic structure of bixbyite a-Mn2O3: a combined density functional theory DFT+U and neutron diffraction study, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.87.184413 (Accessed June 30, 2024)