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

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