Helimagnons in a chiral ground state of the pyrochlore antiferromagnets

Eunsong Choi, Gia Wei Chern, Natalia B. Perkins

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Abstract

The Goldstone mode in a helical magnetic phase, also known as the helimagnon, is a propagating mode with a highly anisotropic dispersion relation. Here we study theoretically the magnetic excitations in a complex chiral ground state of pyrochlore antiferromagnets such as spinel CdCr2O 4 and itinerant magnet YMn2. We show that the effective theory of the soft modes in the helical state possesses a symmetry similar to that of smectic liquid crystals. An overall agreement is obtained between experiments and our dynamics simulations with realistic model parameters. By exactly diagonalizing the linearized Landu-Lifshitz equation in various commensurate limits of the spiral order, we find a low-energy dispersion relation characteristic of the helimagnons. Our calculation thus reveals the first example of helimagnon excitations in geometrically frustrated spin systems.

Original languageEnglish (US)
Article number37004
JournalEPL
Volume101
Issue number3
DOIs
StatePublished - Feb 2013
Externally publishedYes

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