EVOLUTION OF NANOGRAINS AND SOFT MAGNETIC PROPERTIES OF Fe74Cu0.8Nb2.7Si15.5B7 BY ISOTHERMAL ANNEALING

Fe-based alloy of the composition, Fe74Cu0.8Nb2.7Si15.5B7 has been studied thoroughly in order to research the evolution of nanograins and soft magnetic properties. The composition has been significantly deviated from FINEMET type composition given by Fe73.5Cu1Nb3Si13.5B9. It is hard to optimize composition to obtain equally good soft magnetic properties as FINEMET significantly deviating from conventional type alloy. Fe-based alloy of the composition, Fe74Cu0.8Nb2.7Si15.5B7 has been prepared by single roller melt spinning machine. X-ray diffraction studies confirmed that the ribbon is in the amorphous state. Evolution of alpha-Fe(Si) nanograins from amorphous matrix were carried out by isothermal annealing in the temperature range from 550 degrees C to 650 degrees C for 1, 3, 5, 10, 20, 30, 40, 50 and 60 minutes. Frequency spectrum of real and imaginary part of complex initial permeability has been measured for the samples at different annealing conditions. Short time annealing has been proved to be more efficient than long time annealing for the samples of this composition for most of the annealing temperatures.