Magnetic and electrical investigations of Fe85-xCoxB15 metallic glasses

The magnetic and electrical properties of metallic glasses with the general formula Fe85-xCoxB15 were investigated over a large temperature range to study their concentration-dependent physical parameters. All of the samples investigated (x=17,21,30, and 40) were soft ferromagnets with coercive fields Hc≤1 Oe and high Curie temperatures slightly above 1200 K. The temperature-dependent magnetization behaved irregularly, and exhibited hysteresis during heating and subsequent cooling through the Curie temperature. The variation of the magnetization with temperature demonstrates that one or more phase transformations (crystallization) occurred in the course of the heating. The electrical resistivities exhibited positive temperature coefficients and minima at temperatures below 50 K. We did not observe a nonmonotonic variation of the magnetic and electrical properties with a monotonic change of the Fe85-xCoxB15 composition that would correlate with the earlier proposed formation of “strong” nanoclusters in the vicinity of particular stoichiometrically close Fe:Co ratios. The good soft magnetic characteristics make the Fe85-xCoxB15 metal glasses promising candidates for engineering materials in inductive applications.