Enhanced remanence in flash-annealed Nd/sub 4/Fe/sub 78/B/sub 18/

Abstract

A b s t r a c t -N a n o c r y s t a l l i n e N d q F e 7 g B 1 8 w a s produced by affixing current leads directly to amorphous ribbons for flash-annealing. Ribbons were annealed in the range Ta = 650-10OO0C, for times 10-600 s. Flash-annealed ribbons show higher remanence ratios (Mr/Ms 0.83) than those submitted to conventional furnace (68O0C/1O min) annealing ( M r / M e 0.74). In flash-annealed ribbons, Mossbauer spectroscopy and xr a y d i f f~a c~~o n indicated the presence of the Nd2Fe23B3 phase, in addition to Fe3B, NdzFelqB, and a -F e . F l a s h -a n n e a l i n g for short times at high temperatures may give Hc values up to 20% higher than furnace annealing. The isothermal r e m a n e n t magnetization and the dc d e m a g n e t i z a t i o n remanence were found to be in reasonable agreement with the Wohlfarth relation.

Effects of Metastable Phase Formation on the Magnetic Properties of Pr<SUB>4.5</SUB>Fe<SUB>77</SUB>B<SUB>18.5</SUB> Amorphous Ribbons

“…• C. [1][2][3][4][5][6][7][8][9][10] The alloys showing such hard magnetic properties are composed of large amounts of soft magnetic particles such as Fe 3 B, RE 2 Fe 23 B 3 and α-Fe and small amounts of hard magnetic RE 2 Fe 14 B particles exhibiting large magnetocrystalline anisotropy. 9,11,12) The magnetic properties of these alloys depend on the phases precipitated, the grain size, the distribution and the interphase boundary structures between hard and soft magnetic particles.…”

Magnetic interactions in nanocrystalline SmFeCo

“…On the other hand, the deviation was small and oscillatory, as we have observed here, for the low Nd alloy where there is believed to be substantial exchange coupling. An oscillatory Henkel plot was observed for thermally demagnetized nanocrystalline Nd 4 Fe 78 B 18 by Altoé et al 10 This behavior was contrasted to that of MQII which showed strong magnetizing interactions. Thus, an oscillatory Henkel plot has been observed for high remanence materials belonging to the three major systems.…”

“…Henkel plots for an ac demagnetization show both magnetizing and demagnetizing regions, as was observed previously in Nd 9 Fe 85 B 6 ͑␣-FeϩNd 2 Fe 14 B͒ 2 and Nd 4 Fe 78 B 18 . 10 The data were compared to the moving Preisach model. Preliminary calculations indicate the necessity to consider both meanfield and random interactions.…”

“…The Henkel plot obtained for the ac demagnetization showed both magnetizing and demagnetizing interactions as observed in other nanocrystalline magnets. 2, 10 The results were compared with the moving Preisach model.…”

"Novos materiais magnéticos para imãs de alta performance"

“…Kramer and co-workers [5] found that in Rietveld analysis of the X-ray data [6]. 57 Fe Mössbauer spectra were recorded at room temperature, with absorbers made up of ribbons glued side by side on a lucite disk.…”