3847 IEEE TRANSACTIONS ON MAGNETICS, VOL. 33, NO. 5, SEPTEMBER 1997 zyxwvutsrq Formation and Magneto-Structural Properties of the New Nd3Fe29-xWx Intermetallic Phase J. L. Sanchez L1. Lab. de Magnetismo, Facultad de Fisica-IMRE, Universidad de La Habana, La Habana 10400, Cuba. A. C. Neiva, J. M. Marques, F. P. Missell Instituto de Fisica, Universidade de zyxwvutsr Sto Paulo, C.P. 66.3 18, 053 15-970 SBo Paulo, SP, Brazil. H. Salim de Amorin, P. H. Domingues and M. R. Amaral Jr. Instituto de Fisica, Universidade Federal do Rio de Janeiro, C.P. 68.528,21945-970 Rio de Janeiro, RJ, Brazil. Abstract -This work reports the existence of the new ternary phase Nd,Fe2,,W, (monoclinic, prototype Nd,(Fe,Ti),, zyxwvuts ), opening the perspective of a W-stabilized family of compounds. Alloys with starting composition Nd,Fe,,.,W,., were prepared by argon arc melting from pure elements. As-cast ingots were wrapped in tantalum foils and annealed at 1100 "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 zyxwvutsrqp A2/m was successfully assumed. The analysis shows that Nd,(Fe, W)z9 is the main phase (73 wt.%) with lattice parameters a = 10.615(2) zyxwvutsr hi, b = 8.588(2) hi, c = 9.754(2) A and p = 96.74(1)'. It co-exists with Nd,(Fe, W),, (25 wt.%) and a- (Fe, W) (2 wt.%). The thermomagnetic curve of the specimens shows well defined transitions at 72'C and 123'C, which we attribute to the 217 and 3:29 phases, respectively. The composition of the 3:29 compound, measured by EDAX analysis, is Ndl0,,Fe,,,,W4,,. 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 Ndlo,,Fe86,0W,~g. In addition, a small amount of a-(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. I. INTRODUCTION Intensive research during the last two decades has seen the emergence of several families of rare-earth iron transition metal intermetallic compounds with technologically interesting magnetic properties for permanent magnets. The most recent advance in this sense is the RE3(Fe,M)29 system, with RE= rare-earth and M a transition stabilizing metal. Up to now, compounds with the monoclinic Nd,(Fe,Ti),,-type crystal structure have been reported to form with V, Ti, Cr, Mn and MO as stabilizing elements [I], [2]. The monoclinic structure of the 3:29 phase was f i s t described by the P2,Ic Manuscript received February 27, 1997. J. L. Sanchez LI., fax ++53-7-333758, cmater@dialnet.edu.cu; A.C.Neiva, ++Js-l1-8166884, tax +t55-I 14186984, neiva@if.usp.br.; H. Salim de Amorin, fax ++ zyxwvutsrqpon 55- 21- 280 76 93, hsalim@if.ufrj.br. The authors thank to FUJB, FAPERJ, FINEP and CNPq for financial support. space group from both diffraction and neutron diffraction studies [3]-[5]. However, subsequent X-ray diffraction analysis, by Kalogirou, Pycharis, Saettas and Niarchos [6], confirmed by neutron scattering studies by Yellon and Hu [7], showed that the structure is more accurately described by the A2lm space group, which is a minimal non-isomorphic supergroup of the P2,Ic. RE,(Fe, M)29 compounds absorb important amounts of interstitial nitrogen preserving their crystal structure. This leads to a noticeable increase in the Curie temperature and in Sm-compounds a strong uniaxial anisotropy is induced. In fact, Sm,(Fe,M),,N,, with M= Ti, V, Cr, show excellent hard magnetic properties zyxw [8]-[ IO]. This makes the RE3(Fe,-,M,)29 compounds interesting precursors for the development of high-energy bonded magnets. In this paper we report on the existence, structural features and magnetic properties of the novel ternary phase Nd,Fe,,,W,. 11. EXPENMENTAL Alloys with starting composition Nd3Fe27,5W1.5were prepared by arc melting under an argon atmosphere. The purity of the raw materials was 99.9 % for Nd (Aldrich Chemical Co.), 99.95 % for Fe (Alfa Aesar) and 99.98 % for W (Alfa Aesar). The as-cast ingots were wrapped in tantalum foils and annealed in argon at 1100 "C during three weeks. Annealing was followed by quenching in water. Optical microscopy revealed that a small portion of the sample contained unmolten particles of W, surrounded by Fe,W,. This region was cut off and disregarded. Phase structure and composition of the remaining homogeneous regions were investigated by means of X-ray diffraction, DC thermomagnetic (TMA) analysis, SEM and EDAX microprobe. X-ray diffraction (XRD) studies were performed on powdered samples with an automated Siemens type-F diffractometer in step-scanning mode 01-28. The high-voltage was supplied by a high stability Philips PW1830/25 generator. A graphite monochromator was used to select Cu Ka-doublet zyxwv (A = 1.542 A). The linear response of the detection system was strictly teated Cnlibra+ion and alignment conditions were checked with a finely ground sample of a-A120, (1 pm); the angles and intensities were in excellent agreement with the values given by Hubbard, 0018-9464/97$10.00 zyxwvut 0 1997 IEEE