Structural and magnetic properties of annealed [Fe19Ni81]12Å/Ag11Å multilayers studied by Mossbauer spectroscopy, x-ray diffraction and magnetization measurements

The influence of annealing on the properties of an ultrathin permalloy/silver multilayer is analysed using Mossbauer effect, x-ray diffraction, magnetization and magnetoresistance experiments. A thick permalloy him is studied for comparison. From Mossbauer experiments, the existence of a 'magnetically dead' layer is ruled out. An interfacial zone corresponding to about 1.2 monolayers is observed in the low hyperfine held range in the as-deposited film and disappears after annealing at T-a = 450 degrees C, when the layer structure is destroyed. The evolution of the hyperfine held is associated with both densification of the NiFe layers and interface improvement. From Mossbauer and magnetization measurements, the individual Ni and Fe magnetic moments have been evaluated. They exhibit different thermal dependences, in agreement with results on multilayers based on pure Fe or Ni layers.