H.G. Zhang

Recrystallization and magnetic hardening in Mn 1.8 Ga magnet by spark plasma sintering deformation

Theoretical calculations for L1<inf>0</inf>-MnGa compound indicate a high anisotropy constant, K<inf>u</inf> (26 Mergs/cm³) and a saturation magnetization, M<inf>s</inf> (116 emu/g), which predict a maximum energy product, (BH)<inf>max</inf>, of 28 MGOe.

Effect of deformation temperature on crystal texture formation in hot deformed nanocrystalline SmCo 5 permanent magnets

Rare earth-cobalt based magnetic materials have attracted considerable attention due to their large anisotropy eld (H A ), high saturation magnetizations (Ms), and high Curie temperatures (T C ). As the first generation of rare earth-transition metal (RE-TM) based permanent magnet, SmCo 5 possesses extraordinary high anisotropy led over 240 kOe, and nanocrystalline SmCo 5 magnet bears coercivity as high as 50 kOe [1]. Furthermore, the high T C and strong corrosion resistance of nanocrystalline SmCo5 magnet make it a promising candidate for practical application at elevated temperature. Hot deformation technique has been considered as one of the effective way to obtain crystallographic texture and thereby magnetic anisotropy in nanocrystalline permanent magnets. Gabay et al observed enhanced (00l) diffraction peak of SmCo 5 phase in the hot deformed Sm 17 Co 83 magnet [2], indicating a formation of certain degree of crystallographic texture. Yue et al reported that signi-cantly improved texture can be obtained in the nanocrystalline SmCo 5 alloys subjected to die upsetting at a very high degree of deformation (more than 85% height reduction)[3]. However, the mechanism of the plastic deformation and texture formation during the hot deformation process is not clear yet. In this paper, the orientation texture of both grains and their boundary planes in the nanocrystalline SmCo 5 anisotropic magnet have been characterized by using the electron backscattered diffraction (EBSD) technique. Based on these results, effect of deformation temperature on the texture and magnetic properties has been discussed.

Crystal structure and magnetic transition in Fe-Mn-Ga ribbon

Pure bcc β-phase, fcc γ-phase and hcp phase of Fe-Mn-Ga system have been obtained by melt spinning method and subsequent anneal. It is found that there is a rapid phase transition from β and γ-phase to hcp phase. The β-phase shows a typical low temperature ferromagnetic property, while γ-phase shows a ferromagnetic to antiferromagnetic transition. The newly found hcp phase shows a good ferromagnetic behavior with a relatively high TC, which makes it a possible candidate for hard magnetic material.

Disorder-induced enhancement of magnetism in ball-milled Fe 2 CrAl alloy

Chemical ordering has crucial influences on the magnetic and other properties of Heusler alloys [1, 2]. Recently, theoretical investigations predict that highly ordered Fe2CrAl with L21 structure exhibits a half-metallic property with spin polarization of 82%[1]. However, other calculations based on experimental lattice parameters show a non-half-metallic property[2]. Additionally, the theoretical calculation based on L21 structure gives a rather different magnetic moment from the experiment results[1, 3]. It has also been reported by Luo et al[4] that partial disordering on different sites of this alloy will lead to the enhancement of its magnetic moment. Due to these pending issues and the possibility to modulate the magnetic properties of this alloy by different preparation methods, a systematic investigation about the ball-milled Fe2CrAl alloy has been carried out. Significant enhancement of the magnetic properties has been achieved in this system.