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

We report a study on the structural and magnetic properties of iron-vanadiu m thin films grown in multilayer form and mixed by thermal treatment. The m ultilayer was composed of 30 Angstrom Fe layers alternated by 30 Angstrom o f V. This typical bilayer was repeated 15 times. The samples were structura lly characterized by x-ray diffraction (XRD) in the (theta-2 theta) geometr y. The magnetic characterization was made using a conventional alternate gr adient magnetometer (AGM) with the magnetic field applied along the plane o f the film, and by conversion electron Mossbauer spectroscopy (CEMS). This multilayer was annealed at temperatures between 550 and 670 degrees C for 6 0 minutes. The XRD result for the as-deposited multilayer shows a high-degr ee crystallinity, while GEMS suggests an abrupt interface, since no signifi cant contribution from vanadium in iron is observed. After the thermal trea tment, the results from XRD show a phase transformation of the bcc-disorder ed structure (alpha phase) into a tetragonal structure (sigma phase). GEMS results show a magnetic moment reduction for temperatures above 640 degrees C and an order-disorder transition. The magnetic measurements suggest also a phase transformation.