Synthesis Structural and Magnetic Properties of a Novel Series of Intermetallic Compounds Nd_3(Fe_1-xCo_x)_27.5Ti_1.5(x=0, 0.1, 0.2, 0.3, 0.4)

摘要

The synthesis and the study of the structural and magnetic properties of a novel series of intermetallic compounds, with nominal stoichiometry Nd_3(Fe_1-xCo_x)_27.5Ti_1.5(x=0, 0.1, 0.2, 0.3, 0.4) is presented. Especially, the existence of Nd_3(Fe_0.6Co_0.4)_27.5Ti_1.5(x=0.4) extends the solubility limit of Co atoms in the Fe sites of the 3:29 compounds. The Nd_3(Fe,Ti)_29-type structure with monoclinc symmetry (space group A2/m) is dominant in all samples, with some Nd(Fe,Co,Ti)_12 as a secondary phase and a small amount of alpha-Fe(Co). The unit cell volume is decreasing as the Co content increases. Howeve,r the cell parameters show anisotropic decrease with the Co content. The Curie temperature increases monotonically with x, from 437 to 876 K for the 3:29 phase, and from 553 to 918 K for the 1:12 secondary phase. The saturation magnetisation increases with x from 143.3 for x=0 to 175.5 Am~2/kg for x=0.3 and then decreases to 167.8 for x=0.4. The ansiotropy field increases from 3.7 T for x=0 up to 5.2 T for x=0.2 and then remains constnat. For x>0.2 and at room temperature the compounds present an easymagnetisation direction along the (40-2) direction.