Effect of 'hardness' at the parametric excitation of spin-waves in antiferromagnetic MnCO₃

Abstract

The parametric excitation of spin-waves was studied in the easy-plane antiferromagnet MnCO3 at a microwave pumping frequency wP/2r = 33.8 GHz and T = 1.6 K. The experiments were performed for oblique orientation of the magnetic field H with respect to the basd plane of the crystal. W e found that the two &Rerent microwave threshold fields for the appearance ( & I ) and disappearance (h,z) of parmetric excitation aa well as the 'coefficient of hardness' IC = (&I -hC*)/&x strongly depend on the angle 9 between H and the basal plane, showing a decrease with increasing 9. Our experimental results can be explained by the assumption that some part of the spin-wave relaxation and hardness effect arise from an interaction of spin-waves with 'orthogonal' magnetic impurities.