Exchange stiffness and magnetic anisotropies in bcc Fe1−xCox alloys

TLDR: The saturation magnetization of the alloys was measured independently through superconducting quantum interference device magnetometry as mentioned in this paper, and the magnetic field dependence of the spin wave spectrum as well as the inplane directional dependence of surface magnon were determined.

Abstract: Brillouin scattering measurements from several bcc Fe1−xCox epitaxial films are reported. The magnetic‐field dependence of the spin‐wave spectrum as well as the in‐plane directional dependence of the surface magnon are determined. The saturation magnetization of the alloys was measured independently through superconducting quantum interference device magnetometry. Self‐consistent fitting of the magnon dispersions determined from the separate Brillouin experiments provide values for the concentration dependence of the exchange stiffness D, the fourth‐order crystalline cubic anisotropy K1, and surface anisotropies Ks and Ks,p. In agreement with ferromagnetic resonance data, K1 is found to change sign for x beyond about 35 at. % while D steadily increases with cobalt concentration up to x∼0.5 and subsequently decreases in two Co‐rich samples.