Journal Article

FZJ-2017-07932

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Pseudo-Goldstone Magnons in the Frustrated S=3=2 Heisenberg Helimagnet ZnCr2Se4with a Pyrochlore Magnetic Sublattice

Tymoshenko, Y. V. ; Onykiienko, Y. A. ; Müller, T. ; Thomale, R. ; Rachel, S. ; Cameron, A. S. ; Portnichenko, P. Y. ; Efremov, D. V. ; Tsurkan, V. ; Abernathy, D. L. ; Ollivier, J. ; Schneidewind, A.FZJ* ; Piovano, A. ; Felea, V. ; Loidl, A. ; Inosov, D. S. (Corresponding author)

2017
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/16127  doi:10.1103/PhysRevX.7.041049

Abstract: Low-energy spin excitations in any long-range ordered magnetic system in the absence of magnetocrystallineanisotropy are gapless Goldstone modes emanating from the ordering wave vectors. Inhelimagnets, these modes hybridize into the so-called helimagnon excitations. Here we employ neutronspectroscopy supported by theoretical calculations to investigate the magnetic excitation spectrum of theisotropic Heisenberg helimagnet ZnCr2Se4 with a cubic spinel structure, in which spin-3=2 magnetic Cr3þions are arranged in a geometrically frustrated pyrochlore sublattice. Apart from the conventionalGoldstone mode emanating from the ð0 0 qhÞ ordering vector, low-energy magnetic excitations in thesingle-domain proper-screw spiral phase show soft helimagnon modes with a small energy gap of∼0.17 meV, emerging from two orthogonal wave vectors ðqh 00Þ and ð0 qh 0Þ where no magnetic Braggpeaks are present. We term them pseudo-Goldstone magnons, as they appear gapless within linear spinwavetheory and only acquire a finite gap due to higher-order quantum-fluctuation corrections. Our resultsare likely universal for a broad class of symmetric helimagnets, opening up a new way of studying weakmagnon-magnon interactions with accessible spectroscopic methods.

Keyword(s): Basic research (1st) ; Magnetism (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Streumethoden (JCNS-2)

Research Program(s):

1. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)

Experiment(s):

1. PANDA: Cold three axes spectrometer (SR2)

Appears in the scientific report 2017

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Database coverage:
; ; ; ; Current Contents - Physical, Chemical and Earth Sciences ; DOAJ Seal ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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