纳米复合永磁合金Nd_9Fe_(85-x)Mn_xB_6的结构和磁性

Magnetic properties and microstructures of nanocomposite

利用X射线衍射(XRD)和X射线吸收精细结构(XAFS)技术对淬火速度为20 m/s的退火和未退火Nd9Fe85-xMnxB6(x=0,0.5和1.0)样品分别进行了晶体结构和Fe原子局域环境的分析,并用振动样品磁强计分析了样品的磁性。结果表明:退火前,掺杂微量Mn原子对纳米复合Nd-Fe-B磁性材料的晶体结构和近邻配位无序度都有显著影响,随着Mn含量的增加,Nd2Fe14B硬磁相和α-Fe软磁相的结晶度明显增加;在温度为973 K、5min退火后,Nd9Fe85-xMnxB6(x=0,0.5和1.0)磁体的主相结构基本相同,但矫顽力由339 kA/m增加到398 kA/m,我们认为这是由于掺杂的Mn原子影响Nd2Fe14B和α-Fe颗粒晶界的交换耦合作用所致。

The structures and magnetic properties of the as-spun and annealed Nd9Fe85-xMnxB6 (x=0, 0.5, 1.0) nano-composite magnetic materials were investigated by XRD, XAFS and vibrating sample magnetometer (VSM). The XRD and XAFS results indicated that the structures of the as-spun Nd-Fe-B nano-composites were largely correlated by the addition of element Mn. With increasing the amount of element Mn, the long-range order of both soft magnetic phase a-Fe and hard magnetic phase Nd2Fe14B largely increased. After annealed at the optimal temperature of 973 K for 5 min, the results implied that the long-range and local structures of the Nd9Fe85B6 were almost the same as those of Nd9Fe84 5Mn0.5B6 and Nd9Fe84Mn1B6. However, the VSM results showed that the coercivity was obviously enhanced from 339 to 398 kA/m for the annealed Nd9Fe85-xMnxB6 nano-composites with the x from 0 to 1. These results were supposed to arise from the exchange coupling between the Nd2Fe14B and α-Fe grains induced by the addition of element Mn.