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arXiv · 2001.09917

Nanoscale degeneracy lifting in a geometrically frustrated antiferromagnet

Benjamin A. Frandsen·Emil S. Bozin·Eleni Aza·Antonio Fernandez Martinez·Mikhail Feygenson·Katharine Page·Alexandros Lappas
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Abstract

The local atomic and magnetic structures of the compounds $A$MnO$_2$ ($A$ = Na, Cu), which realize a geometrically frustrated, spatially anisotropic triangular lattice of Mn spins, have been investigated by atomic and magnetic pair distribution function analysis of neutron total scattering data. Relief of frustration in CuMnO$_2$ is accompanied by a conventional cooperative symmetry-lowering lattice distortion driven by Néel order. In NaMnO$_2$, however, the distortion has a short-range nature. A cooperative interaction between the locally broken symmetry and short-range magnetic correlations lifts the magnetic degeneracy on a nanometer length scale, enabling long-range magnetic order in the Na-derivative. The degree of frustration, mediated by residual disorder, contributes to the rather differing pathways to a single, stable magnetic ground state in these two related compounds. This study demonstrates how nanoscale structural distortions that cause local-scale perturbations can lift the ground state degeneracy and trigger macroscopic magnetic order.

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Benjamin A. Frandsen, Emil S. Bozin, Eleni Aza, Antonio Fernandez Martinez, Mikhail Feygenson, Katharine Page, Alexandros Lappas. 2020-01-27. Nanoscale degeneracy lifting in a geometrically frustrated antiferromagnet. https://doi.org/10.1103/physrevb.101.024423

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