Magnetic Properties and Crystallization Kinetics of a Mn-Doped FINEMET Precursor Amorphous Alloy

摘要

The kinetics of nanocrystallization of a Mn-doped FINEMET alloy from its amorphous precursor is reported. The alloy studied was of a composition (Fe(1-x)Mn(x)) (73.5)Nb3CuSi(13.5)B9 where chi = 005. X-ray diffraction (XRD) confirmed that alpha-FeSi is the product of primary nanocrystallization. Crystallization kinetics were studied using time-dependent magnetization, M(t), as a measure of the volume fraction crystallized. This data was taken using vibrating sample magnetometry (VSM) and thermal analysis employing differential scanning calorimetry (DSC). Primary crystallization for the Mn-doped FINEMET alloy was found to occur at 505 deg. C, for DSC data taken at a heating rate of 10 deg C/min. Fits to the Kissinger equation for constant heating transformations yield an activation energy for crystallization of 3.4 eV. VSM measurements of isothermal M(t) show that the maximum volume fraction transformed was reached at 20 min. Measurements of magnetic anisotropy as a function of time probe the structural evolution of the material upon nanocrystallization. Measurements show stress relaxation occurring at 20 minutes at 490 deg. C, coinciding with the maximum volume fraction crystallized.