DYNAMIC LOSSES IN NANOCRYSTALLINE FINEMET FOR VARIOUS ANNEALING TEMPERATURE

The influence of thermal treatments on the dynamical magnetic properti es of finemet ribbons was investigated. The amorphous ribbons of compo sition Fe73.5Cu1Nb3Si13.5B9 have been annealed at various temperatures . Above their crystallization temperature homogenous, nanocrystalline of-FeSi grains with grain diameter of 3-12 nm have been produced. The total energy loss density for frequencies from 20 Hz to 50 kHz and pol arizations from 0.2 to 0.9 T was measured and subdivided into hysteres is loss and dynamic loss. For annealing temperatures from 500 to 580-d egrees-C and 1 h annealing time a broad minimum in the hysteresis loss es occurs and splitting up into two minima for high polarizations. The dynamic losses show deeper minima at nearly the same annealing temper atures. The total losses in the region of the broad minimum of the hys teresis losses are mainly determined by the dynamic losses. For anneal ing temperatures over 590-degrees-C the total losses are mainly determ ined by the hysteresis losses. For 0.2 T polarization amplitude and hi gh frequencies the decrease of the anomaly factor with increasing freq uency is extraordinarily high.