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arXiv · 1507.01740

Magnetic order, spin waves and fluctuations in the triangular antiferromagnet La2Ca2MnO7

P. Dalmas de Réotier·C. Marin·A. Yaouanc·T. Douce·A. Sikora·A. Amato·C. Baines
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Abstract

We report magnetic susceptibility, specific heat and muon spin relaxation (muSR) experiments on the triangular antiferromagnet La2Ca2MnO7 which develops a genuine two-dimensional, three-sublattice \sqrt{3} \times \sqrt{3} magnetic order below T_N = 2.8 K. From the susceptibility and specific heat data an estimate of the exchange interaction is derived. A value for the spin-wave gap is obtained from the latter data. The analysis of a previously reported inelastic neutron scattering study yields values for the exchange and spin-wave gap compatible with the results obtained from macroscopic measurements. An appreciable entropy is still missing at 10 K that may be ascribed to intense short-range correlations. The critical paramagnetic fluctuations extend far above T_N, and can be partly understood in terms of two-dimensional spin-wave excitations. While no spontaneous muSR field is observed below T_N, persistent spin dynamics is found. Short-range correlations are detected in this temperature range. Their relation to a possible molecular spin substructure and the observed exotic spin fluctuations is discussed.

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P. Dalmas de Réotier, C. Marin, A. Yaouanc, T. Douce, A. Sikora, A. Amato, C. Baines. 2015-07-07. Magnetic order, spin waves and fluctuations in the triangular antiferromagnet La2Ca2MnO7. https://doi.org/10.1142/s2010324715400019

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