A Potential Co36Fe36Si4B20Nb4 nanocrystalline alloy for high temperature soft magnetic applications

The paper addresses the structural, crystallization, soft magnetic and Curie temperature behaviour of Co36Fe36Si4B20Nb4 alloy. The material, prepared in the
form of ribbons by melt-spinning technique, was amorphous in the as-cast state. Differential scanning calorimetry (DSC) showed two stages of crystallization whereas thermal variation of electrical resistivity (TER) carried out to a higher range of temperature indicated three stages of crystallization. The first crystallization stage, which occurred at 845K and 825K in DSC and TER, respectively,
was due to the formation of nanophase (CoFe)2Si as evidenced by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The formation of these nanoparticles reduced the magnetocrystalline anisotropy,
thereby revealing good soft magnetic properties in the samples annealed between 825K and 875K with coercivity less than 49.9Am1 (627 mOe) and susceptibility0.72103. In this optimum nanocrystalline state, the material
also exhibited a high Curie temperature above 1100 K, opening the scope of the present nanocrystalline alloy for high temperature applications.