Emergence of order in nanocrystalline SmFe9

2019-11-09 02:49:02

temperature TA TC deg SmFe9

责任者: Djega-Mariadassou, C.;Bessais, L. 单位: LCMTR, CNRS, Thais, France 来源出处: Journal of Magnetism and Magnetic Materials(J. Magn. Magn. Mater. (Netherlands)),2000/02/,210(1-3):81-7 摘要: Three samples consistent with 1:12, 2:17 and 1:7 stoichiometry, ball-milled and subsequently annealed at temperature Ta between 600 and 1200°C were studied by Rietveld analysis, coupled to Curie temperature Tc measurements and Mossbauer spectroscopy. For all samples, at 600°C⩽Ta<900°C, the detected out-of-equilibrium phase is the hexagonal P6/mmm structure derived from TbCu7 with the composition SmFe9. At Ta⩾900°C the ordered R3¯m phase of Th2Zn17-type is observed. With increasing Ta the unit cell parameter small variation of the parent SmFe9 induces a decrease of Tc and ⟨Hhf⟩. For Ta=600°C SmFe9 is defined by a=0.4919 nm, c=0.4162 nm, Tc=207°C and ⟨Hhf⟩=232 kOe. The resulting ordered Sm2Fe17 is characterized by a=0.4941√(3) nm, c=3×0.4147 nm, Tc=144°C and ⟨Hhf⟩=219 kOe. For Ta=750°C the SmFe9 Tc is 171°C associated to ⟨Hhf⟩=222 kOe 关键词: annealing;Curie temperature;ferromagnetic materials;iron alloys;lattice constants;Mossbauer effect;nanostructured materials;order-disorder transformations;permanent magnets;powder metallurgy;samarium alloys;nanocrystalline magnet;stoichiometry;ball-milling;annealing;temperature dependence;Rietveld analysis;Curie temperature;Mossbauer spectroscopy;out-of-equilibrium phase;hexagonal structure;ordered phase;unit cell parameter;XRD;X-ray diffraction;magnetization;hyperfine field;600 to 1200 C;SmFe9