%0 Journal Article
%T Softened magnetic excitations in the s = 3/2 distorted triangular antiferromagnet alpha-CaCr2O4
%A Dirk Wulferding
%A Kwang-Yong Choi
%A Peter Lemmens
%A Alexey N. Ponomaryov
%A Johan van Tol
%A A. T. M. Nazmul Islam
%A Sandor Toth
%A Bella Lake
%J Physics
%D 2012
%I arXiv
%R 10.1088/0953-8984/24/43/435604
%X 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{\deg} phase. As an origin we discuss a complex spin topology formed by four inequivalent nearest neighbor and sizable next-nearest neighbor interactions.
%U http://arxiv.org/abs/1205.3640v2