Eur. Phys. J. B (2015) 88: 64
https://doi.org/10.1140/epjb/e2015-60033-6

Regular Article

Lifetimes of magnons in two-dimensional diluted ferromagnetic systems

Institut für Theoretische Physik, Univeristät Regensburg, 93040 Regensburg, Germany

^a e-mail: akash.chakraborty@physik.uni-regensburg.de

Received: 12 January 2015
Received in final form: 4 February 2015
Published online: 16 March 2015

Abstract

Spin dynamics in low dimensional magnetic systems has been of fundamental importance for a long time and has currently received an impetus owing to the emerging field of nanoelectronics. Knowledge of the spin wave lifetimes, in particular, can be favorable for future potential applications. We investigate the low-temperature spin wave excitations in two-dimensional disordered ferromagnetic systems, with a particular focus on the long wavelength magnon lifetimes. A semi-analytical Green’s functions based approach is used to determine the dynamical spectral functions, for different magnetic impurity concentrations, from which the intrinsic linewidth is extracted. We obtain an unambiguous q⁴ scaling of the magnon linewidth which is ascribed to the disorder induced damping of the spin waves, thereby settling a longstanding unresolved issue on the wave-vector dependence. Our findings are also in good agreement with previous theoretical studies on Heisenberg ferromagnets. Additionally, we demonstrate the futility of using the low moments associated with the spectral densities to evaluate the magnon dispersions and lifetimes.