Antiferromagnetic resonance and magnetic structure of GdAs

Electron spin resonance measurements on single-crystal and powder of GdAs have been performed in the temperature range from 4.2 to 40 K and in the frequency range from 55 to 585 GHz to obtain microscopic information about the magnetic structure. The results obtained indicate that GdAs is an "easy-plane" antiferromagnet with the magnetic moment lying in the (111) plane below Neel temperature (similar to 20 K). According to an analysis of mean field approximation, the exchange field and the out-of-plane anisotropy field have been estimated to be mu(0)H(E) = 8.1T and mu(0)H(A) = 1.4T, respectively. The transition field (H-c = 2H(E) + H-A) from the antiferromagnetic to the forced ferromagnetic state is 17.6 T.