Mn-20Ga纳米复合磁性材料的制备和磁性能研究

Fabrication and Magnetic Properties of Mn-20Ga Nanocomposite Magnetic Materials

Mn-Ga合金具有高矫顽力和较高的磁晶各向异性,是一类具有较大发展前景的磁性材料。采用机械合金化方法制备Mn-20Ga(at%,下同)纳米磁性复合材料,复合材料在300~415℃,2~8 h进行退火。重点研究了磁性相种类、纳米晶尺寸和磁性能随退火条件的变化规律。研究发现,未退火的Mn-20Ga合金主要组成相为纯Mn与纯Ga,退火后Mn-20Ga合金的主要磁性相为纳米级尺寸的Mn3Ga相和Mn0.85Ga0.15相,另含有少量氧化导致的MnO_(2)相。适当地提高退火温度,可促进剩磁、矫顽力与磁能积的提高,延长退火时间也有利于剩磁和磁能积的提高。在385℃时进行6 h的热处理,可获得最佳的磁性能:剩磁63.21 kA/m、矫顽力648 kA/m、磁能积1.2 kJ/m^(3)。适当提高保温温度和/或延长保温时间,可使Mn_(0.85)Ga_(0.15)相的尺寸减小,并与矫顽力升高的趋势相一致。Mn_(0.85)Ga_(0.15)相晶粒尺寸的减小有利于提高合金的磁性能。

The Mn-Ga alloy displays high coercivity and a relatively large magnetic anisotropy. These characteristics suggest that it is a good potential magnetic material for the future. Herein, we prepared Mn-20 Ga(at%, the same below) nanocomposite magnetic materials through mechanical alloying using high-energy ball milling. The samples were annealed at a temperature range from 300 ℃ to 415 ℃ for a holding time range from 2 h to 8 h. This study focused on the variation of magnetic phases types, nanocrystalline size and magnetic properties with annealing conditions. The results show that the main phases of the unannealed Mn-20 Ga alloy are pare Mn and Ga, the main magnetic phases in Mn-20 Ga magnetic material after annealing are nano-sized Mn3 Ga and Mn0.85 Ga0.15, in addition to a small amount of MnO_(2) phase caused by oxidation. The remanence, coercivity, and maximum magnetic energy product can be improved by enhancing the annealing temperature into a proper range.Extending the annealing time properly is also beneficial to the improvement of remanence and maximum magnetic energy product. The optimal magnetic properties in this research are obtained at annealing temperature of 385 ℃ for 6 h, which show a remanence of 63.21 kA/m, a coercivity of 648 kA/m, and a maximum magnetic energy product of 1.2 kJ/m^(3). The size of Mn_(0.85)Ga_(0.15) nanophase can be decreased by a proper enhancement of annealing temperature and annealing time, which corresponds to the increase of coercivity. The decrease of Mn_(0.85)Ga_(0.15) crystal size is beneficial to the enhancement of magnetic properties of the alloy.