HIGH TEMPERATURE MAGNETIC PROPERTIES OF PARTIALLY RE-CRYSTALLIZED COBALT SUBSTITUTED FINEMET-TYPE ALLOYS

摘要

Partial re-crystallization of amorphous FeSiB alloys with small additions of Nb and Cu (Fmemet) is well known to lead to a fine grained composite consisting of nanometer-sized particles of Fe(Si) embedded in a magnetic amorphous matrix. These materials are magnetically soft at room temperature with coercivities as low as 0.01 Oe. At modest temperatures of only about 300℃, however, the amorphous matrix becomes nonmagnetic, the ferromagnetic coupling between the Fe(Si) particles decreases, and the coercivity increases. Motivated by a number of technological applications requiring soft magnetic materials in high temperature environments, we have prepared, characterized, and studied Co substituted Finemet-type alloys with compositions of (Fe_xCo_(100-x))_(73.5)Si_(13.5)B_9Cu_1Nb_3, where x = 50,75, and 100 at. %, with the goal of preserving the desirable room temperature magnetic properties of Finemet at higher temperatures. The results of these studies show that an enhanced magnetization can be achieved without a significant increase in the coercivity for the cobalt substituted alloys.