Magnetic soft modes in the locally distorted triangular antiferromagnet   alpha-CaCr2O4
  In this paper we explore the phase diagram and excitations of a distorted triangular lattice antiferromagnet. The unique two-dimensional distortion considered here is very different from the 'isosceles'-type distortion that has been extensively investigated. We show that it is able to stabilize a 120{\deg} spin structure for a large range of exchange interaction values, while new structures are found for extreme distortions. A physical realization of this model is \alpha-CaCr2O4 which has 120{\deg} structure but lies very close to the phase boundary. This is verified by inelastic neutron scattering which reveals unusual roton-like minima at reciprocal space points different from those corresponding to the magnetic order. 
S. Toth, B. Lake, K Hradil, T. Guidi, K. C. Rule, M. B. Stone, A. T.   M. N. Islam
cond-mat.str-el