Theoretical description of spin waves in disordered materials
Sprache des Vortragstitels:
DPG Spring Meeting 2019 Regensburg
Sprache des Tagungstitel:
In order to study spin waves in disordered materials, we present two theoretical approaches based on a Heisenberg model. Both complement each other in the description of magnon properties in spin systems with disorder of arbitrary kind and concentration of impurities. Firstly, magnons in systems with substitutional (uncorrelated) disorder can be efficiently calculated within a single-site coherent potential approximation for the Heisenberg model. From the computational point of view, this method has several advantages, is inexpensive, and directly applicable to systems like alloys and doped materials. We show that it performs exceedingly well across all concentrations and wave vectors. However, we need another approach for more complex systems like layers forming island or short-range order. Therefore, we will present a second possibility using a configurational average over possible realizations of large supercells in direct numerical simulations. The effective interaction between magnetic moments entering the Heisenberg model in both methods can be obtained from first-principles using a self-consistent Green function method within the density functional theory. Thus, our method can be viewed as an ab initio approach and can be used for calculations of magnons in real materials.