Spin-reorientation transition in nano-, micro- and single-crystalline Nd{sub 2}Fe{sub 14}B
- Institute for Experimental Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna (Austria)
Spin reorientation of Nd{sub 2}Fe{sub 14}B with different degree of grain sizes was detected by measuring the temperature dependence of the ac susceptibility. The studied materials include: (1) a spherical Nd{sub 2}Fe{sub 14}B single crystal that shows no coercivity. (2) Microcrystalline Nd{sub 2}Fe{sub 14}B obtained by induction-melting or by sintering: Due to the presence of random-oriented multi-domain grains ({ge}5000 nm), the bulk ingot shows no coercivity, but sintered materials do. (3) Microcrystalline Nd{sub 2}Fe{sub 14}B produced by the hydrogenation-disproportionation-desorption-recombination (HDDR): The HDDR treated materials show a coercivity due to the presence of single-domain grains of a size of about 200{endash}300 nm. (4) Nanocrystalline Nd{sub 2}Fe{sub 14}B prepared by mechanical alloying and by rapid quenching: Due to the presence of ultrafine Nd{sub 2}Fe{sub 14}B grains ({lt}50nm), these materials show a high coercivity and an enhanced remanence. For the first time, a decrease of the spin-reorientation temperature, an intrinsic magnetic property, with decreasing the Nd{sub 2}Fe{sub 14}B grain size is found. The decrease of the spin-reorientation temperature in nanocrystalline Nd{sub 2}Fe{sub 14}B can be ascribed to the strong inter-grain exchange change coupling among nanocrystalline Nd{sub 2}Fe{sub 14}B. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 496480
- Report Number(s):
- CONF-961141-; ISSN 0021-8979; TRN: 97:016177
- Journal Information:
- Journal of Applied Physics, Vol. 81, Issue 8; Conference: 41. annual conference on magnetism and magnetic materials, Atlanta, GA (United States), 12-15 Nov 1996; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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