Structural and magnetic properties of Fe thin films onCu90Au10(001)

Abstract

A series of Fe thin films with thicknesses ranging from 1 monolayer (ML) to 30 ML was deposited on a ${\mathrm{Cu}}_{90}{\mathrm{Au}}_{10}$ (001) substrate $(a=3.66 \AA{})$ at room temperature. Structural properties were investigated by low-energy electron diffraction (LEED). From intensity vs energy [I(E)] measurements of the specular LEED reflection, three different structural phases were observed. The first phase at low Fe thicknesses $(l4 \mathrm{ML})$ is a tetragonally expanded fcc phase (fct) with an interlayer distance ${a}_{\ensuremath{\perp}}$ above $1.90 \AA{}.$ The second phase at Fe thicknesses between 4 and 10 ML is associated with an interlayer distance ${a}_{\ensuremath{\perp}}\ensuremath{\approx}1.76 \AA{}.$ With further increasing Fe thickness $(g10 \mathrm{ML}),$ the third phase, a bcc(011) structure with ${a}_{\ensuremath{\perp}}\ensuremath{\approx}2.03 \AA{},$ occurs. The magnetic properties were studied by in situ magneto-optical Kerr effect (MOKE). It was found that the Fe films of the first and third phase have a high-spin ferromagnetic moment, while they exhibit a low net magnetic moment in the second phase. The observed structural and magnetic phases are thus similar to the Fe/Cu(001) system. The direction of the easy magnetic axis in ${\mathrm{F}\mathrm{e}/\mathrm{C}\mathrm{u}}_{90}{\mathrm{Au}}_{10}$ is perpendicular to the film plane only at thicknesses below 2 ML, where a spin-reorientation transition from perpendicular-to-the-film-plane to in-plane with increasing film thickness has been found. The origin of perpendicular magnetization is discussed.