FORMATION AND MAGNETOSTRUCTURAL PROPERTIES OF THE NEW ND3FE29-XWX INTERMETALLIC PHASE

This work reports the existence of the new ternary phase Nd3Fe29-xWx ( monoclinic, prototype Nd-3(Fe,Ti)(29)), opening the perspective of a W -stabilized family of compounds. Alloys with starting composition Nd3F e27.5W1.5 were prepared by argon are melting from pure elements. As-ca st ingots were wrapped in tantalum foils and annealed at 1100 degrees C during three weeks followed by quenching in water. The homogeneous r egion of the best sample was characterized by structural and magnetic measurements. X-ray diffraction patterns were analyzed by the Rietveld method. For the 3:29 structure the space group A2/m was successfully assumed. The analysis shows that Nd-3(Fe, W)(29) is the main phase (73 wt.%) with lattice parameters a = 10.615(2) Angstrom, b = 8.588(2) An gstrom, c = 9.754(2) Angstrom and beta = 96.74(1)degrees. It co-exists with Nd-2(Fe, W)(17) (25 wt.%) and alpha-(Fe, W) (2 wt.%). The thermo magnetic curve of the specimens shows well defined transitions at 72 d egrees C and 123 degrees C, which we attribute to the 2:17 and 3:29 ph ases, respectively. The composition of the 3:29 compound, measured by EDAX analysis, is Nd10.1Fe85.6W4.3. The average composition of the hom ogeneous region, calculated from the composition (measured by EDAX ana lysis) and weight fractions (calculated by Rietveld analysis of the XR D patterns) of the phases, is Nd10.1Fe86.0W3.9. In addition, a small a mount of alpha-(Fe, W) is detected. The saturation magnetization was e stimated as 102 emu/g. The temperature dependence of the saturation ma gnetization and AC susceptibility are reported. Tile latter shows a ma gnetic anomaly at 259 K which suggests the existence of a spin reoriet ation transition.