MAGNETIC AND STRUCTURAL-PROPERTIES OF NANOCRYSTALLINE ULTRATHIN FE83CU1NB7B9 SUBMITTED TO JOULE HEATING

Ultrathin (similar to 10 mu m) ribbons of the amorphous alloy Fe38Cu1N b7B9 obtained by single roll melt spinning have been submitted to de J oule heating in vacuo in order to develop a nanocrystalline phase char acterised by a very reduced grain size. The initial permeability of th e nanocrystallized alloy was measured on open samples by means of a co nventional fluxmetric technique with air-flux compensation. The interv al of magnetising frequency was 100 Hz - 10 kHz. All samples were subm itted to X-ray diffraction to evaluate the mean grain size, compositio n and strain level of the nanocrystalline phase. A substantial improve ment in the magnetic permeability of Joule-heated nanocrystalline samp les with respect to the conventionally annealed ones has been always f ound. Variations as high as 1000 times the as-quenched value have been observed for a wide range of electrical-current densities (4 10(7) le ss than or equal to j less than or equal to 6 10(7) A/m(2)).