Static magnetic measurements have been carried out on single crystals of Er2Fe14B and Tm2Fe14B in a temperature range between 77 and 590 K. Spin reorientation phenomena have been found in both compounds slightly above room temperature. In Er2Fe14B, the easy direction of magnetization changes from [100] to [001] at 316 K as temperature increases, and Tm2Fe14B from [100] to [001] at 310 K. Anomalously large anisotropy in the saturation magnetization has been detected around the spin reorientation temperature. 相似文献
Y2Fe14B and Nd2Fe14B are ferromagnets in which 3d interactions are dominant. In Y2Fe14B, the -axis of the quadraticque est de magnetization. The 3d anisotropy is an order of magnitude weaker than in YCo5. In agreement with point-charge model, CEF potential in Nd2Fe14B favours the -axis at 300 K. At low temperature, the magnetization reorientation observed results from competition between exchange and anisotropy. 相似文献
The magnetic properties of Nd4.5Fe77−xMnxB18.5 (x=0, 1 and 2) nanocomposites prepared by the crystallization of amorphous precursors were investigated. Addition of Mn is found to decrease the crystallization temperature of the amorphous ribbons. The intrinsic coercivity iHc and maximum energy product (BH)max increase from 2.6 kOe and 9.1 MGOe for x=0 to 3.1 kOe and 10.3 MGOe for x=1, respectively, and the remanence ratio Mr/Ms increases from 0.70 to 0.72. The effect of Mn on Curie temperature TC and the thermal stability of Mr and iHc were also studied. 57Fe Mössbauer spectra have been recorded for x=0, 1 and 2 ribbons at room temperature and site preference of the Mn atoms in Fe3B and Nd2Fe14B phases is discussed using the Mössbauer spectroscopy. 相似文献
It is difficult to obtain the crystallographic alignment for stoichiometric Nd2Fe14B alloys by applying the melt-spun and subsequent hot-pressing and hot-deformation techniques. However, the enhanced alignment and magnetic properties of die-upset nano-crystal Nd2Fe14B magnets have been obtained by Nb addition in the present paper. The magnetic properties studies show that Nb addition leads to the remarkable increase of remanence Br and intrinsic coercivity Hci, which is due to the improvement of c-axis texture and refinement of microstructure. Microstructure studies using transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that Nb atoms are enriched at grain boundary and the NbFeB phase is observed with increasing Nb content. Since some Fe atoms in the Nd2Fe14B phase participate in the formation of NbFeB phase, the excessive Nd atoms may be enriched at grain boundary, which may improve the physical property of grain boundary and provide a mass transport pass for preferential growth of oriented Nd2Fe14B grains, thus leading to the enhanced alignment and magnetic properties. 相似文献
In this paper, compact bulk nanocomposite Nd2Fe14B/α-Fe magnetic materials were prepared by hot extrusion of amorphous and nanocrystalline powders, which were prepared by high-energy ball-milling (HEBM) of the Nd2Fe14 B-type hard magnetic phase with 20 vol% of α-Fe as soft magnetic phase. The extrusion temperature has important influence on magnetic properties and microstructure of magnetic materials. The results show that the grain size of Nd2Fe14B and α-Fe phase increases steadily with increasing extrusion temperature. Furthermore, optimal extrusion temperature of 1223 K occurs, at which the highest magnetic properties and relative density can be obtained. 相似文献
The lean rare-earth Pr4.5Fe77−xTixB18.5 (x=0, 1, 4, 5) nanocomposite alloys were prepared by melt spinning method and subsequent thermal annealing. The effect of Ti content and annealing temperature on the magnetic properties and the microstructure of these magnets were investigated. The enhancing coercivity Hc from 211.4 to 338.2 kA/m has been observed at the optimal annealing temperature of 700 °C by the addition of 5 at% Ti in Pr2Fe14B/Fe3B alloys. It was also found that increasing Ti content leads to marked grain refinement in the annealed alloys, resulting in strong exchange-coupling interaction between the hard and the soft phases in these ribbons. In addition, the magnetization reversal behaviors of Pr2Fe14B/Fe3B nanocomposites were discussed in detail. 相似文献
