Field dependence of uniform magnon energies in lamellar CoCl2 and CoBr2 by AFMR experiments

Abstract AFMR experiments in the frequency range 77 v GHz and in the magnetic field range 0 H kG on antiferromagnetic CoCl 2 and CoBr 2 single crystals at 4.2 K are reported. The waves propagate along the c axis of the crystals and the steady magnetic field is in the plane of the layers, which is also the easy plane of the spins. The influence of a rotation of the field in the easy magnetization plane is investigated, showing the existence of antiferromagnetic domains. The results of the field dependence of uniform magnon energies are reported in detail for the two compounds CoCl 2 and CoBr 2 . In CoBr 2 , the two magnon modes at zero field are non degenerate, their frequencies are v 1 (0) = 60 GHz and v 2 (0) = 675 GHz , and the field required for saturation is H s ⊥ = 74.2 kG .