Observation of antiferromagnetic resonance affected by hyperfine interaction in GdBi

Electron spin resonance (ESR) measurements on a single crystal of GdBi have been performed in the temperature range from 50 to 1.7 K at the frequency range between 58 and 107 GHz to obtain the microscopic information about the magnetic properties. The absorption line of ESR corresponding to (formula presented) of the (formula presented) ion is observed at temperatures between 50 and 10 K. With decreasing temperature from 7 K, the absorption line shifts to lower field side. The results obtained indicate that the shift in resonance field is due to a temperature-dependent anisotropy field arising from hyperfine interaction of Gd spin with the Bi nuclear moments. The estimated values of the anisotropy field and the hyperfine anisotropy field are (formula presented) and (formula presented) respectively, at 4.2 K.