Helical spin-waves, magnetic order, and fluctuations in the langasite compound Ba3NbFe3Si2014

Stock, C.; Chapon, L.C.; Su, Y.; Schneidewind, A.; Cheong, S.-W.; Lee, N.; McMorrow, D.F.; Bombardi, A.; Radaelli, P.G.

doi:10.1103/PhysRevB.83.104426

Journal Article

Helical spin-waves, magnetic order, and fluctuations in the langasite compound Ba3NbFe3Si2014

Stock, C. ; Chapon, L. C. ; Schneidewind, A. ; Su, Y.FZJ* ; Radaelli, P. G. ; McMorrow, D. F. ; Bombardi, A. ; Lee, N. ; Cheong, S.-W.

2011
APS College Park, Md.

Physical review / B 83(10), 104426 (2011) [10.1103/PhysRevB.83.104426]

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Please use a persistent id in citations: http://hdl.handle.net/2128/10931 doi:10.1103/PhysRevB.83.104426

Abstract: We have investigated spin fluctuations in the langasite compound Ba3NbFe3Si2O14 both in the ordered state and as a function of temperature. The low-temperature magnetic structure is defined by a spiral phase characterized by magnetic Bragg peaks at (q) over right arrow = (0,0,tau similar to 1/7) onset at T-N = 27 K as previously reported by Marty et al. [Phys. Rev. Lett. 101, 247201 (2008)]. The nature of the fluctuations and temperature dependence of the order parameter is consistent with a classical second-order phase transition for a two-dimensional triangular antiferromagnet. We show that the physical properties and energy scales including the ordering wave vector, Curie-Weiss temperature, and spin waves can be explained through the use of only symmetric exchange constants without the need for a dominant Dzyaloshinskii-Moriya interaction. This is accomplished through a set of "helical" exchange pathways along the c direction imposed by the chiral crystal structure and naturally explains the magnetic diffuse scattering, which displays a strong vector chirality up to high temperatures, well above the ordering temperature. This illustrates a strong coupling between magnetic and crystalline chirality in this compound.

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

Classification:

Physics, Condensed Matter

Note: We are grateful to A. Orszulik (ISIS) and H. Schneider (JCNS) for expert technical support throughout the experiments and to R. Coldea and R. Cowley for helpful discussions. We are indebted to J. Jensen for very helpful comments and suggestions. We are also grateful for grants from the EU-NMI3 Access Program for partial funding of this research. The work at Rugers was supported by the National Research Foundation of Korea (Grant No. KRF-2008-220-C00012).

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Appears in the scientific report 2011

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