FERROMAGNETIC-RESONANCE STUDIES OF AMORPHOUS AND NANOCRYSTALLINE FECUNBSIB ALLOYS

Alloys with composition Fe73.5Cu1Nb3Si22.5-xBx, where x = 6 and 9, hav e been studied from the as-cast state, through various stages of cryst allization, in annealing range of 300-650 degrees C, by the technique of ferromagnetic resonance (FMR). The annealing was performed isotherm ally at preset temperatures to produce nanocrystalline structures in a n amorphous matrix. Both the nanocrystalline structures and the surrou nding amorphous matrix are ferromagnetic, and will therefore contribut e to the FMR spectra. The spectral features, resonance field, intensit y, and linewidth have been used to characterize the structurally relat ed changes in the sample during the crystallization process. The major changes in the spectra are observed to occur in the region of the cry stallization peak in the differential thermal analysis curves for thes e samples. The FMR spectra exhibit a complex in-plane angular variatio n, which is understood in terms of preferential orientation of the mag netization vector in the direction of the ribbon, and shape effects. T he square cut samples give rise to multipeaked spectra when the extern al magnetic field is applied in an ''off-square'' direction. This is t he first report of the appearance of a second resonance feature of thi s type. This is explained as arising from the magnetic confinement of the nanocrystallites in the amorphous matrix, producing spin waves loc alized at the interface of the two phases. (C) 1997 American Institute of Physics.