Parallel Pumping of Spin-Waves in an Orthorhombic Antiferromagnet

Abstract

By means of the parallel pumping technique, unstable growths of spin-waves are observed in antiferromagnetic CuCl₂2H₂O at a pumping frequency of 8.912 GHz. The threshold rf-field h_c for the onset of parallel pumped spin-wave instability is theoretically obtained for antiferromagnets with the anisotropy of orthorhombic type. In addition to excitation of two spin-waves of the same branch in the spin-wave spectrum, excitation of two spin-waves of the different branches is also considered. The threshold field h_c is experimentally obtained for the low-frequency branch when the static and the rf-fields are both applied parallel to the spin easy axis. Using the theoretical expression for h_c, the experimental data are deduced to the spin-wave linewidth ΔH_k which increases linearly with k² for small k and is proportional to T^4.6 in the temperature range from 1.2 to 1.8 K.