Formation and magnetic properties of TbCu{sub 7}-type RFe{sub 7} compounds and their nitrides (R=Tb and Dy)
- 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-; ISSN 0021-8979; TRN: 97:016246
- 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
Similar Records
Structural and hard magnetic properties of rapidly solidified Sm--Fe--N
Coherent precipitation in the TbCu{sub 7}-type GdCo-based ribbons prepared by simple processing