The effect of Nb additions on the thermal stability of melt-spun Nd{sub 2}Fe{sub 14}B
- Department of Applied Science, Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)
- Magnequench International, Inc., 6435 Scatterfield Road, Anderson, Indiana 46013 (United States)
Elevated-temperature superconducting quantum interference device (SQUID) magnetometry was performed on two samples of melt-spun and optimally annealed Nd{sub 2}Fe{sub 14}B; one sample contained 2.3 wt{percent} Nb and one was Nb-free. Continuous full hysteresis loops were measured with a SQUID magnetometer at T=630K, above the Curie temperature of the 2{endash}14{endash}1 phase, as a function of field (1T{le}H{le}{minus}1T) and time on powdered samples sealed in quartz tubes at a vacuum of 10{sup {minus}6}Torr. The measured hysteresis signals were deconstructed into a high-field linear paramagnetic portion and a low-field ferromagnetic signal of unclear origin. While the saturation magnetization of the ferromagnetic signal from both samples grows with time, the signal from the Nb-containing sample is always smaller. The coercivity data are consistent with a constant impurity particle size in the Nb-containing sample and an increasing impurity particle size in the Nb-free sample. The paramagnetic susceptibility signal from the Nd{sub 2}Fe{sub 14}B-type phase in the Nb-free sample increases with time, while that from the Nb-containing sample remains constant. It is suggested that the presence of Nb actively suppresses the thermally induced formation of poorly crystallized Fe-rich regions that apparently exist in samples of both compositions. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 347051
- Journal Information:
- Journal of Applied Physics, Vol. 85, Issue 8; Other Information: PBD: Apr 1999
- Country of Publication:
- United States
- Language:
- English
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