Thermal annealing effects on the structural and magnetic properties ofFe/V multilayers

Abstract

We report a study on the structural and magnetic properties of iron-vanadiumthin films grown in multilayer form and mixed by thermal treatment. Themultilayer was composed of 30 Å Fe layers alternated by 30 Å of V. Thistypical bilayer was repeated 15 times. The samples were structurallycharacterized by x-ray diffraction (XRD) in the (θ-2θ)geometry. The magnetic characterization was made using a conventionalalternate gradient magnetometer (AGM) with the magnetic field applied alongthe plane of the film, and by conversion electron Mössbauer spectroscopy(CEMS). This multilayer was annealed at temperatures between 550 and 670 °C for 60 minutes. The XRD result for the as-deposited multilayershows a high-degree crystallinity, while CEMS suggests an abrupt interface,since no significant contribution from vanadium in iron is observed. After thethermal treatment, the results from XRD show a phase transformation of thebcc-disordered structure (α phase) into a tetragonal structure(σ phase). CEMS results show a magnetic moment reduction fortemperatures above 640 °C and an order-disorder transition. Themagnetic measurements suggest also a phase transformation.