Antiferro-quadrupole resonance in CeB6
  We report experimental observation of a new type of magnetic resonance caused by orbital ordering in a strongly correlated electronic system. Cavity measurements performed on CeB6 single crystals in a frequency range 60-100 GHz show that a crossing of the phase boundary TQ(B) between the antiferro-quadrupole and paramagnetic phases gives rise to development at T <TQ(B) of a magnetic resonance. The observed mode is gapless and correspond to g-factor 1.62. 
S.V. Demishev, A.V. Semeno, A.V.Bogach, Yu.B. Paderno, N.Yu.   Shitsevalova, N.E. Sluchanko