Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.
The double hard magnetic phase magnets with nominal compositions of Nd30–xDyxFe69B1（x=2, and 4）（wt.%） were prepared. The magnetic properties of the magnets were measured with a NIM-2000H hysteresigraph. The crystalline structures of the magnets were identified by X-ray diffraction（XRD）. The Rietveld refinement was carried out using the FULLPROF software. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） analyses were carried out in order to investigate the microstructure of the magnets. It showed that the magnets consisted mainly of Nd2Fe14 B phase, and some Nd-rich phase. Two types of matrix-phase grains in dark grey and light grey were found in the magnets with x=2 and 4. The Dy content was obviously different in the two types of grains, which proved that the double hard magnetic phases（Dy-rich and Dy-lean phases） coexisted in the magnet. It revealed that the Nd-rich phases in junction regions had fcc structure, with the unit cell parameter of about 0.52–0.56 nm. The weak superlattice spots were found in the SAD patterns of the junction Nd-rich phases with large scale. The double hard magnetic phase structure seemed to improve the magnetic properties of NdFeB magnets with high coercivity, while decrease the consumption of Dy element, compared with the single alloy magnet.
Anisotropic CeCo4.325_xCuo.675Fex （x ： 0.475- 0.875） sintered magnets were prepared by traditional powder metallurgical method. Influence of ball-nfilling time and iron content on microstructure and magnetic properties of the CeCo4,325-xCuo.675Fex sintered magnets were investigated. It is shown that the properties of the magnet produced by mag- netic powders ball-milled for 40 min are better than that for 30 rain. With iron content increasing, remanence Br and maxi- mum energy product （BH）m increase first and then decrease. The optimal magnetic properties are obtained for the CeCo3.65Cuo.675Feo.675 sintered magnet： Br=0.685 T, the intrinsic coercivity Hci = 350 kA.m-1, and （BH）m ： 85.6 kJ.m-3. The increase of Br is mainly influenced by iron content of 1：5 matrix which can properly increase the saturation induction Bs; the rapid increase of the amount of Ce-rich phase and 5：19 phase gives rise to the deterioration of the magnets when x ≥ 0.775.
Wei SunMing-Gang ZhuYi-Kun FangWei PanMan-Long XiaWei Li
Nanomagnetism is the origin of many unique properties in magnetic nanomaterials that can be used as building blocks in information technology, spintronics, and biomedicine. Progresses in nanomagnetic principles, distinct magnetic nanostructures, and the biomedical applications of nanomagnetism are summarized.
A multifunctional material with both electrorheological（ER） performance and luminescence property was synthesized by a simple coprecipitation. The tetrabutyl titanate, as well as the Tb（NO3）3·6H2O and sulphosalicylic acid（C7H6O6S·2H2O, SSA） were chosen as starting materials. The composition, ER performance and luminescence property of the material were studied. The results showed that a novel material（TiTbSSA） with both ER performance and luminescence property was obtained. The relative shear stress τr（τr=τE/τ0, τE and τ0 were the shear stresses of the suspension with and without an applied electric field） of the suspension（30 wt.%） of the material in silicone oil reached 32.7 at a shear rate of 12.5 s–1 and an electric field strength of 4 kV/mm（DC electric field）. The material containing the rare earth（RE=Tb） complex exhibited fine luminescence performance and higher ER activity. Therefore, it is a novel multifunction material which would have wide application prospect.
