Flash annealing and magnetic interactions in Pr4Fe78B18

Abstract

Enhanced-remanence Pr4Fe78B18 alloys were produced by using a high heating rate/short time anneal, known as flash annealing. Partially amorphous ribbons were produced by melt spinning and then annealed for 10–20 s at temperatures 600–820 °C by passing current through the sample. Coercivity increases of up to 15% were systematically observed in relation to furnace-annealed material. Mössbauer spectra showed that flash annealing resulted in significant amounts of Pr2Fe23B3 and reduced quantities of α-Fe. Our best flash-annealed material (600 °C/20 s) had Hc=3.5 kOe, Mr/Ms=0.77, and (BH)max=11.1 MG Oe. The magnetic remanence curves Mr(H), obtained for different initial demagnetized states (thermal, ac, dc+, dc−), and the remanence Md(H), obtained for an initially saturated state, were determined for the construction of Henkel plots (HP). The HP for ac and thermally demagnetized Pr4Fe78B18 are very similar and show both magnetizing and demagnetizing interactions. There is no significant difference between the HP of furnace and flash-annealed samples.