Journal of Magnetism and Magnetic Materials 272–276 (2004) 1493–1494 Effects of Zr and Ti substitutions on the crystallization processes of Fe 3 B/Nd 2 Fe 14 B nanocomposite magnetic system A. Jianu a , M. Valeanu a, *, D.P. Lazar a , F. Lifei a , C. Bunescu a , V. Pop b a National Institute for Materials Physics, P.O. Box Mg-7, 76900 Bucharest, Romania b Faculty of Physics, Babes-Bolyai University, 3400 Cluj-Napoca, Romania Abstract The influence of Zr and Ti substitutions on the formation of a nanocomposite magnet was studied by high- temperature X-ray diffraction and magnetic measurements. It has been shown that Ti and especially Zr additions favorably change the crystallization temperatures and the sequence of phase transformations which leads to an exchange coupled magnet, even in a composition range that promotes the precipitation of the detrimental Nd 2 Fe 23 B 3 phase. r 2003 Elsevier B.V. All rights reserved. PACS: 75.50.Vv; 75.30.Et; 75.50.Kj; 81.40.Rs Keywords: Nd–Fe–B nanocomposite; Crystallization process; Metastable phase In nanocomposite Nd 2 Fe 14 B/a-Fe or Fe 3 B permanent magnets the magnetic properties are deeply related to the microstructure. An optimum structure consists of uniformly distributed soft- and hard-magnetic nano- phases. In practice, it is difficult to control the grain size; in many cases, microalloying elements (e.g. Cu, Nb, Ga, W, and Si [1,2]) have been used to optimize the microstructure. In this work the microalloying effects of Zr and Ti substitution on the evolution of crystallization process and the magnetic hardening of the Nd 7 Fe 81 B 12 alloy have been studied. Ingots with nominal compositions Nd 7 Fe 81 B 12 , Nd 7 Fe 81 Ti 2 B 10 and Nd 7 Fe 79 Zr 2 B 12 were prepared by arc melting. Amorphous ribbons (25 mm thickness) were obtained by melt spinning in argon atmosphere. The temperature-induced crystallization processes were studied in situ using synchrotron radiation in high- temperature energy-dispersive X-ray diffraction experi- ments (HASY-LAB, F2.1 beam line). Phase composi- tion and magnetic behavior were analyzed on samples heated for 2–5min, in vacuum, at temperatures between 650  C and 800  C. Conventional XRD measurements were performed using Cu Ka radiation. Hysteresis loops were obtained by the extraction method at room temperature, in fields up to 1.8T, applied along the length of the ribbons. High-temperature energy-dispersive X-ray diffraction (EDXRD) using synchrotron radiation was performed for the evaluation of phase transformations process. Fig. 1 shows the diffraction patterns of the substitution- free sample in the temperature range 300–850  C. It is to note that the Nd fluorescence lines at 36.84, 37.36, 42.27 and 43.32keV are superposed to the diffraction spectra. The crystallization process starts at 600  C with the precipitation of the Nd 2 Fe 23 B 3 metastable phases which was detected as a predominant phase even at the highest temperature. The first diffraction peaks of the Nd 2 Fe 14 B phase become visible at 700  C. The selected composi- tion has the stoichiometry near that of the Nd 2 Fe 23 B 3 phase. A lack of composition gradient around meta- stable phase grains induces a low rate of atomic diffusion. This may explain the high value of the decomposition temperature. For the Nd 7 Fe 81 Ti 2 B 10 sample, the crystallization also starts at 600  C with the formation of Nd 2 Fe 23 B 3 , but this phase decomposes into Fe 3 B and Nd 2 Fe 14 B at ARTICLE IN PRESS *Corresponding author. E-mail address: valeanu@alpha1.infim.ro (M. Valeanu). 0304-8853/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.1005