Direct observation of low energy nuclear spin excitations in HoCrO$_3$   by high resolution neutron spectroscopy
  We have investigated low energy nuclear spin excitations in strongly correlated electron compound HoCrO$_3$. We observe clear inelastic peaks at $E = 22.18 \pm 0.04$ $\mu eV$ in both energy loss and gain sides. The energy of the inelastic peaks remains constant in the temperature range 1.5 - 40 K at which they are observed. The intensity of the inelastic peak increases at first with increasing temperature and then decreases at higher temperatures. The temperature dependence of the energy and intensity of the inelastic peaks is very unusual compared to that observed in other Nd, Co and V compounds. Huge quasielastic scattering appears at higher temperatures presumably due to the fluctuating electronic moments of the Ho ions that get increasingly disordered at higher temperatures. 
T. Chatterji, N. Jalarvo, C.M.N. Kumar, Y. Xiao and Th. Br\"uckel
cond-mat.str-el