First-principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys

Abstract

Heusler alloys have been intensively studied due to the wide variety of properties that they exhibit. One of these properties is of particular interest for technological applications, i.e., the fact that some Heusler alloys are half-metallic. In the following, a systematic study of the magnetic properties of three different Heusler families ${\mathrm{Co}}_{2}\mathrm{Mn}\mathrm{Z},{\text{Co}}_{2}\text{Fe}\text{Z}$, and ${\mathrm{Mn}}_{2}\mathrm{V}\mathrm{Z}$ with $\text{Z}=\left(\text{Al,}\phantom{\rule{4.pt}{0ex}}\text{Si,}\phantom{\rule{4.pt}{0ex}}\text{Ga,}\phantom{\rule{4.pt}{0ex}}\text{Ge}\right)$ is performed. A key aspect is the determination of the Gilbert damping from first-principles calculations, with special focus on the role played by different approximations, the effect that substitutional disorder and temperature effects. Heisenberg exchange interactions and critical temperature for the alloys are also calculated as well as magnon dispersion relations for representative systems, the ferromagnetic ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ and the ferrimagnetic ${\mathrm{Mn}}_{2}\mathrm{V}\mathrm{Al}$. Correlation effects beyond standard density-functional theory are treated using both the local spin density approximation including the Hubbard $U$ and the local spin density approximation plus dynamical mean field theory approximation, which allows one to determine if dynamical self-energy corrections can remedy some of the inconsistencies which were previously reported for these alloys.