Abstract
-CaCr2O4 is a spin-3/2, distorted triangular lattice antiferromagnet with a simple 120 spin
structure that masks the complex pattern of exchange interactions. The magnetic excitation spectrum
has been measured using inelastic neutron scattering on powder and single crystal samples.
It reveals unusual low energy modes which can be explained by linear spin-wave theory assuming
nearest and next-nearest neighbor interactions. The mode softening is due to the next-nearest
neighbor interactions and indicates a new magnetic phase nearby as revealed by the phase diagram
constructed for this system. The extracted direct exchange interactions correlate well with the
Cr3+{Cr3+ distances and are in agreement with other chromium oxide delafossite compounds.
