Formation and magnetic properties of TbCu{sub 7}-type RFe{sub 7} compounds and their nitrides (R=Tb and Dy)

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

DOI:https://doi.org/10.1063/1.365190· OSTI ID:496554

Yang, J; Mao, O; Altounian, Z ^[1]

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1. Department of Physics, Center for the Physics of Materials, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (CANADA)

DyFe{sub x} and TbFe{sub x} alloys with x=7, 7.7, and 9 were mechanically alloyed followed by annealing in an attempt to prepare TbCu{sub 7}-type DyFe{sub 7} and TbFe{sub 7} compounds. X-ray-diffraction and thermomagnetic measurements show that single-phase TbCu{sub 7}-type TbFe{sub 7} can be obtained for all three compositions, while DyFe{sub 7} was formed for x=7.7 and 9 when annealed in the temperature range from 650 to 850{degree}C. The Curie temperature (T{sub c}) of the TbCu{sub 7}-type phase shows no obvious variation with Fe content, but decreases with annealing temperature. For DyFe{sub 7.7} and TbFe{sub 7.7}, their respective Curie temperatures are reduced from 160 and 185{degree}C by annealing at 700{degree}C for 3 h to 140 and 160{degree}C after annealing at 850{degree}C for 3 h. Magnetometry measurements reveal that the TbCu{sub 7}-type phase is a soft phase with a room-temperature coercivity of less than 500 Oe. Nitriding the TbCu{sub 7}-type phase results in lattice expansions without changing the crystal structure. However, nitriding increases the Curie temperatures dramatically to 465 and 450{degree}C for TbFe{sub 7.7}N{sub y} and DyFe{sub 7.7}N{sub y}, respectively. Furthermore, nitriding greatly enhanced the coercivities of TbCu{sub 7}-type compounds, reaching values of 3.75 and 4.0 kOe for TbFe{sub 7.7}N{sub y} and DyFe{sub 7.7}N{sub y}, respectively. The nitrides with optimum coercivities are single-phase TbCu{sub 7}-type compounds with an average grain size of 10{endash}15 nm as estimated from Bragg peak broadening. A coercivity mechanism based on contributions from the random anisotropy of the R{sup 3+} ions and the crystalline anisotropy is proposed to explain the observed effects.{copyright} {ital 1997 American Institute of Physics.}

• OSTI ID: 496554
• 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
ANISOTROPY
ANNEALING
COERCIVE FORCE
CURIE POINT
DYSPROSIUM ALLOYS
DYSPROSIUM NITRIDES
FERROMAGNETIC MATERIALS
GRAIN SIZE
IRON ALLOYS
MAGNETIC PROPERTIES
PHASE STUDIES
SURFACE HARDENING
TERBIUM ALLOYS
TERBIUM NITRIDES
X-RAY DIFFRACTION