Structural characterization and magnetoimpedance effect in amorphous and nanocrystalline AlGe-substituted FeSiBNbCu ribbons.

چکیده مقاله

Abstract
Two series of rapidly solidified FINEMET (Fe73.5Si13.5B9Nb3Cu1) alloys with and without partial substitution of Al (1.5 at%)/Ge
(1 at%) were prepared by melt-spinning technique. The nanocrystallization process was carried out by the heat treatment of the as-spun
ribbons at 560 1C for 1 h in a vacuum furnace. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning
calorimeter (DSC), Mo¨ ssbauer spectroscopy, and magnetoimpedance (MI) measurements were conducted on the as-quenched and heattreated
alloys to investigate their structural and magnetic properties. The average crystallite sizes obtained for the heat-treated samples
were in the range of 10–12nm as confirmed by our XRD and TEM data. The ultrasoft magnetic behavior observed for the Al/Gesubstituted
nanocrystalline alloys was confirmed both by our magnetic data and magnetoimpedance ratio (MIR%) results. A twofold
increase in the magnitude of the MIR% (99%) was observed for the Al/Ge-substituted nanocrystalline alloy against that of the pure
FINEMET alloy (48%) measured at 5.5 MHz. This is believed to be related to the decrease of the magnetocrystalline anisotropy as well
as magnetostriction decline due to the Al substitution for Fe atoms in this nanostructured alloy.