Structure, spin-dynamics, and magnetic properties of annealed nanoscaled Fe layers on GaAs
Justin M. Shaw, Charles M. Falco
We performed a detailed study of the effect of annealing (at temperatures up to 300°C) on 0.2-3.0 nm thick epitaxial Fe layers deposited on GaAs(001). Using Brillouin light scattering, we studied the magnetic properties and spin dynamics of these layers and find a strong correlation between magnetic properties and the structure and chemical properties, as measured with electron diffraction, scanning tunneling microscopy, and x-ray photoemission spectroscopy. We found that significant changes in crystallinity and microstructure occur with annealing. Specifically, annealing of the thinnest layers results in the formation of a discontinuous magnetic layer with increased crystal order. At slightly larger thicknesses, faceted pits form in the Fe layer. This change in structure results in an earlier transition to a ferromagnetic phase, the creation of an additional higher frequency spin-wave mode, and a reduction in the magnetic uniaxial anisotropy constant.