Substrate dependent reduction of Gilbert damping in annealed Heusler alloy thin films grown on group IV semiconductors

Abstract

A structural and FMR study is presented for epitaxial thin films of the Heusler alloy Co 2 FeAl 0.5 Si 0.5 (CFAS) grown on Ge(111) and Si(111) substrates. All films, as-grown and post-annealed, show B2 ordering; full chemical order (L2 1 ) is not obtained over the range of anneal temperatures used in this study. As-grown films show a lower Gilbert damping constant, a, when grown on a Si(111) substrate compared to Ge(111). Annealing the films to 450 C significantly reduces a for CFAS on Ge while increasing a for CFAS on Si. This is related to a substrate dependent competition between improvements in lattice structure and increased interfacial intermixing as a function of anneal temperature. The optimal annealing temperature to minimize a is found to differ by $100 K between the two substrates. Above an anneal temperature of 500 C, films grown on both substrates have increased coercivity, decreased saturation magnetization, and show characteristic two-magnon scattering features.

Elucidation of orbital moment, anisotropy, and magnetic damping in epitaxial Fe3O4 films

“…For the annealed sample the magnetic damping is still dominated by two magnon scattering (TMS) which is indicative of magnetic inhomogeneities. In particular, a peak in the linewidth as a function of frequency is observed in the FMR data which has only been previously seen in spherical samples [8] or samples with small intrinsic Gilbert damping in combination with TMS [9]. We show than this non-monotonic behavior is consistent with a small out-of-plane tilting of the magnetization in combination with TMS.…”

“…As a result, the in-plane resonance field should display six-fold symmetry with the in-plane easy axes along the 〈12 ̅ 1〉 directions for negative Kc. The cubic contribution to the measured anisotropy for a flat (111) film is small, with variations in the resonance field on the order of a few 10's Oe [24]. In-plane uniaxial anisotropy should not be present in a pure cubic system.…”

Absence of spin-mixed states in ferrimagnet Yttrium iron garnet

“…All VNA-FMR measurements were performed at an RF power of +7 dBm. Linescans at constant frequency were extracted from the FMR frequency-field maps and fitted using an asymmetric Lorentzian function 15 to determine the corresponding resonance field (H r ).…”