Magnetic damping in sputtered Co2MnGe Heusler compounds with A2, B2 and L21 order: Experiment and Theory
Justin M. Shaw, Eric R. Edwards, Martin A. Schoen, Michael L. Schneider, Matthew R. Pufall, Thomas J. Silva, Hans T. Nembach, Erna Delczeg
We show that very low values of the magnetic damping parameter can be achieved in sputter deposited poly-crystalline films of Co2MnGe annealed at relatively low temperatures ranging from 240 oC to 400 oC. Damping values as low as 0.0014 are achieved with an intrinsic value of 0.0010 after spin-pumping contributions are taken into account. Of importance to most applications is the low value of inhomogeneous linewidth that yields measured linewidths of 1.8 mT and 5.1 mT at 10 GHz and 40 GHz, respectively. The damping parameter is found to monotonically decrease as the B2 order of the films increases. This trend is reproduced in calculations of the damping parameter from density functional theory. Here, the damping parameter is calculated as the structure evolves from A2 to B2 to L21 orders. The largest decrease in the damping parameter occurs during the A2 to B2 transition as the half-metallic phase becomes established.