ESR measurements of the chiral spin system CuB2O4

Abstract We report ESR measurements of the chiral spin system CuB 2 O 4 at 35 GHz in H ∥ c . The g -value is determined as 2.16 for the c -axis. Anomalies in the resonance field and the line width have been observed around 21 and 9 K, which correspond to the successive phase transitions. In the helimagnetic state, a small hysteretic dip appears in ESR spectrum in addition to a helimagnetic resonance absorption. The dip shifts rapidly to the higher field with decreasing temperature below the transition temperature at 9 K.