Formation and magneto-structural properties of the new Nd/sub 3/Fe/sub 29-x/W/sub x/ intermetallic phase

This work reports the existence of the new ternary phase Nd/sub 3/Fe/sub 29-x/W/sub x/ (monoclinic, prototype Nd/sub 3/(Fe,Ti)/sub 29/), opening the perspective of a W-stabilized family of compounds. Alloys with starting composition Nd/sub 3/Fe/sub 27.5/W/sub 1.5/ were prepared by argon arc melting from pure elements. As-cast ingots were wrapped in tantalum foils and annealed at 1100/spl deg/C during three weeks followed by quenching in water. The homogeneous region 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/sub 3/(Fe,W)/sub 29/ is the main phase (73 wt.%) with lattice parameters a=10.615(2) /spl Aring/, b=8.588(2) /spl Aring/, c=9.754(2) /spl Aring/ and /spl beta/=96.74(1)/sup 0/. It co-exists with Nd/sub 2/(Fe,W)/sub 17/ (25 wt.%) and /spl alpha/-(Fe,W) (2 wt.%). The thermomagnetic curve of the specimens shows well defined transitions at 72/spl deg/C and 123/spl deg/C, which we attribute to the 2:17 and 3:29 phases, respectively. The composition of the 3:29 compound, measured by EDAX analysis, is Nd/sub 10.1/Fe/sub 85.6/W/sub 4.3/. The average composition of the homogeneous region, calculated from the composition (measured by EDAX analysis) and weight fractions (calculated by Rietveld analysis of the XRD patterns) of the phases, is Nd/sub 10.1/Fe/sub 86.0/W/sub 3.9/. In addition, a small amount of /spl alpha/-(Fe,W) is detected. The saturation magnetization was estimated as 102 emu/g. The temperature dependence of the saturation magnetization and AC susceptibility are reported. The latter shows a magnetic anomaly at 259 K which suggests the existence of a spin reorientation transition.