ELECTRICAL-RESISTIVITY BETWEEN 10-K AND 1000-K OF FERROMAGNETIC CO75SI25-XBX AND CO100-X(SI0.6B0.4)X AMORPHOUS RIBBONS

The study of the variation of the electrical resistivity ρ between 10 and 1000 K has been performed in the Co75Si 25-xBx and Co1 00-x(Si0.6B0.4) x ferromagnetic amorphous series. A general analysis of the curves gives useful data about the main features of ρ in these materials: Curie temperatures Tc, temperatures of the minima Tmin, crystallization temperatures Tx, temperature coefficient of resistivity, and absolute resistivity. The correlations between these magnitudes have been discussed including direct comparison with the nonmagnetic Ni-Si-B similar compounds. An analysis of the structural and magnetic contributions to the resistivity is presented in the whole temperature range. The structural part is interpreted in the framework of the extended Ziman model and it is superposed on the magnetic term. A T2 magnetic contribution coming from the spin wave scattering is found at temperatures between Tmin and approximately 0.5 Tc. At higher temperatures, the magnetic part seems to be understood taking into account the mean field approximation. Saturation magnetization M(T) measurements over 300 K were carried out in order to get an experimental hint of the correlation between the magnetic ρ and M(T) with rather satisfactory results. Besides the general analysis we report the achievement of a progressive shift of Tmin in some compounds (in particular in Co70Si18B 12) in which a tentative explanation might be based on phonon ineffectiveness arguments.