EFFECT OF CRYSTALLIZATION ON MAGNETIC DOMAIN-STRUCTURE OF THINNED AMORPHOUS FESIBCUNB RIBBONS

Crystallization and associated magnetic domain structure of Fe73.5CU1N b3Si13.5B9 amorphous ribbons have been investigated in insitu annealin g studies by electron transmission microscopy (TEM), Two stages of cry stallization, which occurred at 380 degrees C and 650 degrees C, have been observed. The crystals associated with these temperatures are sph erical nuclei with diameters less than 5 nm or clusters of ultrafine g rains whose diameters are in the range of 15-20 nm respectively. The p roducts formed at both stages are identified as the alpha-Fe(Si) phase . The magnetic domain structure of the as-quenched specimen is compose d of large and simple domains. There is no evident change in domain st ructure upon the onset of the first crystallization. However, the seco nd stage of crystallization leads to emergence of magnetic ripple. The origin of magnetic ripple is discussed within the framework of the ra ndom anisotropy model. From the analysis, effective uniaxial anisotrop y < k > in the nanocrystalline alloy may be considered as local random anisotropy and is therefore likely to be the cause of the magnetic ri pple. The estimated mean wavelength, lambda, of the magnetic ripple is approximately 160 nm.