Structural and magnetic investigation of gradually devitrified Nanoperm alloys

Abstract Time and temperature evolution of structural and magnetic properties of gradually devitrified NANOPERM-type alloy of composition Fe 84 Nb 3.5 Zr 3.5 B 8 Cu 1 has been studied using differential scanning calirometery (DSC), X-ray diffraction (XRD), Mossbauer spectroscopy and magnetic measurements. XRD and Mossbauer measurements reveal that thermal annealing (as a function of both time and temperature)-induced nanocrystallization leads to the formation of an Fe-rich bcc phase with a small amount of boron, while other non-magnetic elements like Nb, Zr and majority of B remain in the residual amorphous matrix. Grain diameter of the nanocrystalline phase ranges between 7 and 10 nm and their volume fraction ranges between 15% and 48%. Increase of annealing temperature as well as time affects the coercive field considerably. The lowest value of the coercive field, 6 Am −1 (corresponding saturation magnetization value is 1.4 T), is obtained after annealing the sample at 530 °C for 1 h, ascribed to the increased exchange coupling between the nanograins.