FLASH ANNEALING AND MAGNETIC-INTERACTIONS IN PR4FE78B18

Enhanced-remanence Pr4Fe78B18 alloys were produced by using a high hea ting rate/short time anneal, known as flash annealing. Partially amorp hous ribbons were produced by melt spinning and then annealed for 10-2 0 s at temperatures 600-820 degrees C by passing current through the s ample. Coercivity increases of up to 15% were systematically observed in relation to furnace-annealed material. Mossbauer spectra showed tha t flash annealing resulted in significant amounts of Pr2Fe23B3 and red uced quantities of alpha-Fe. Our best flash-annealed material (600 deg rees C/20 s) had H-c = 3.5 kOe, M-r/M-s = 0.77, and (BH)(max) = 11.1 M G Oe. The magnetic remanence curves M-r(H), obtained for different ini tial demagnetized states (thermal, ac, dc(+), dc(-)), and the remanenc e M-d(H), obtained for an initially saturated state, were determined f or 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 betwee n the HP of furnace and flash-annealed samples. (C) 1997 American Inst itute of Physics.