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arXiv · 1205.3640

Softened magnetic excitations in the s = 3/2 distorted triangular antiferromagnet alpha-CaCr2O4

Dirk Wulferding·Kwang-Yong Choi·Peter Lemmens·Alexey N. Ponomaryov·Johan van Tol·A. T. M. Nazmul Islam·Sandor Toth·Bella Lake
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Abstract

The spin dynamics and magnetic excitations of the slightly distorted triangular s = 3/2 system alpha-CaCr2O4 are investigated by means of Raman spectroscopy and electron spin resonance (ESR) to elucidate its peculiar magnetic properties. Two-magnon excitations in circular RL symmetry show a multi-maximum structure with a dominant spectral weight at low energies. The temperature dependence of the ESR linewidth is described by a critical broadening DeltaHpp(T) ~ (T - T_N)^{-p} with the exponent p = 0.30(3) - 0.38(5) for temperatures above T_N = 42.6 K. The exponent is much smaller than that of other s = 3/2 triangular lattices. This is ascribed to soft roton-like modes, indicative of the instability of a helical 120° phase. As an origin we discuss a complex spin topology formed by four inequivalent nearest neighbor and sizable next-nearest neighbor interactions.

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Dirk Wulferding, Kwang-Yong Choi, Peter Lemmens, Alexey N. Ponomaryov, Johan van Tol, A. T. M. Nazmul Islam, Sandor Toth, Bella Lake. 2012-10-10. Softened magnetic excitations in the s = 3/2 distorted triangular antiferromagnet alpha-CaCr2O4. https://doi.org/10.1088/0953-8984%2F24%2F43%2F435604

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