Chiral magnetism and helimagnons in a pyrochlore antiferromagnet

Eunsong Choi, Gia Wei Chern, Natalia B. Perkins

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6 Scopus citations

Abstract

Recent neutron scattering measurements on the spinel CdCr2O 4 revealed a rare example of helical magnetic order in geometrically frustrated pyrochlore antiferromagnet. The spin spiral characterized by an incommensurate wave vector Q=2π(0,δ,1) with δ≈0.09 is accompanied by a tetragonal distortion. Here we conduct a systematic study on the magnetic ground state resulting from the interplay between the Dzyaloshinskii-Moriya interaction and further neighbor exchange couplings, two of the most important mechanisms for stabilizing incommensurate spin orders. We compute the low-energy spin-wave spectrum based on a microscopic spin Hamiltonian and find a dispersion relation characteristic of the helimagnons. By numerically integrating the Landau-Lifshitz-Gilbert equation with realistic model parameters, an overall agreement between experiment and the numerical spectrum, lending further support to the view that a softened optical phonon triggers the magnetic transition and endows the lattice a chirality.

Original languageEnglish (US)
Article number054418
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number5
DOIs
StatePublished - Feb 15 2013
Externally publishedYes

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