The compound Sm0.98Fe9.02–xGaxNδ(x=0, 0.25, 0.5, 0.75, 1) were prepared by melt-spun method and subsequent annealing and nitriding. The Rietveld analysis showed that the lattice expansion played an important role in improving the Curie temperature. An obvious development of the Curie temperature was obtained with the increased Ga content from x=0–1(ΔTc=90 oC). The optimum coercivity of nitrides was obtained at x=0.25 with the value Hcj=652 kA/m(8.15 kOe) after annealing, which corresponded to a reasonable distribution of grain sizes of both TbCu7-type SmFe9Nδ and α-Fe. However, an excess of Ga doping might lead to an abnormal growth of α-Fe, which in turn deteriorated the magnetic properties. It was concluded that a moderate Ga content was very effective in raising the coercivity and Curie temperament in the TbCu7-type Sm-Fe-N.
GdNi_5 nanoparticles and GdNi_5/Gd_2O3nanocapsules(with GdNi_5 core and Gd_2O_3 shell) were prepared by arcdischarge technique under different hydrogen partial pressure.The GdNi_5 nanoparticles show irregular spherical shape and have a size distribution of 10—50 nm with an average diameter of 15 nm.In comparison,the GdNi_5/Gd_2O_3 nanocapsules present spherical morphology and show a size distribution of 10—100 nm with an average diameter of 60 nm.Under a magnetic field change of 50 kOe,the maximum magnetic entropy change of GdNi_5 nanoparticles is 13.5 J/(kg K) at 5 K,while the corresponding value of the GdNi_5/Gd_2O_3nanocapsuels is only 5.7 J/(kg K) at 31 K.The origin of the large magnetic entropy change of GdNi_5nanoparticles is ascribed to its high atomic moments and small anisotropy energy barrier induced by its small particle size.
Jun LiSong MaHan WangWenjie GongJingjing JiangShaojie LiYong WangDianyu GengZhidong Zhang
The crystal structure and magnetic properties of SmFe9-x Cox(x = 0, 1, 3, 5) alloys were studied by X-ray powder diffraction(XRD) and magnetic measurements. The Th2 Zn17-type structure of the as-cast state is changed to TbCu7-type structure after quenching to a rotating molybdenum roll under certain velocity(12, 20, and 32 m s-1). The(002) XRD peak appears and a-Fe phase disappears when the Co is added up to x = 5. Saturation magnetization of SmFe9 under different temperature shows 9 % change(112–102 A m2 g-1) when the temperature is higher than 200 K. The saturation magnetization is 115 A m2 g-1and coercivity is 0.304 T at 5 K for SmFe9 alloys. Increased saturation magnetization and decreased coercivity can be obtained for Co added up to x = 5 at 5 K.
Yang LuoDun-Bo YuHong-Wei LiWei-Dong ZhuangKuo-She LiWen-Long Yan
A systematical investigation was carried out on structure and magnetic properties in SmFe_(9-x)V_(x)(x=0.4,0.8,1.2)compounds prepared by a single-roller quenching method.The high cool-down rate leads to metastable TbCu_(7) phase in the parent compound,which gradually transforms into equilibrium ThMn_(12) structure with V-doping content increasing.The Curie temperature increases from 470 to 590 K with V doping,which is consistent with the phase transformation.Surprisingly,simultaneous increase in both coercivity and remanence is resulted by V doping,reaching the highest value of 685 kA·m^(-1)and 44.8×10^(-3)A·m^(2)·g^(-1)in x=1.2 compound,respectively.This phenomenon can be explained by the combination of phase transformation and intergranular exchange coupling throughδM-H plots.
Yong-Jun MaoJin-Ling JinJia-Jun XieYang LuoKuo-She LiWen-Long YanDun-Bo YuHong-Wei Li
