Spin-reorientation transition in nano-, micro- and single-crystalline Nd{sub 2}Fe{sub 14}B

Journal Article · Tue Apr 01 04:00:00 EST 1997 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.364791· OSTI ID:496480

Kou, X C; Dahlgren, M; Groessinger, R; Wiesinger, G ^[1]

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1. 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--
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 81; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ALLOYS
COERCIVE FORCE
DESORPTION
FERROMAGNETIC MATERIALS
GRAIN SIZE
IRON ALLOYS
MAGNETIC SUSCEPTIBILITY
NEODYMIUM ALLOYS
PHASE TRANSFORMATIONS
SPIN ORIENTATION
TEMPERATURE DEPENDENCE