Structural and Hyperfine Evolution of the (Fe79Mn21)1-xCux System under milling time

M. MIZRAHI, A. F. CABRERA Y J. DESIMONI

Buenos Aires

Simposio; 15th International Symposium on Metastable, Amorphous and Nanostructured Materials; 2008

Metastable Fe-based alloys are a research area of growing interest due to the great variety of new properties shown by these kinds of materials, and their potential technological applications. On the other hand, ball milling technique is extensively used to synthesize materials far from thermodynamic equilibrium regime. It is a suitable technique to produce the reduction of crystallite size and atomic disorder leading to several magnetic behaviors. In the last decade, great emphasis has been placed on the nanosized materials to study the unique physical properties that derived from size reduction effects down to the nanodimension and from the surface to bulk ratio that for coarse ones [1]. Frustration of the exchange interactions, disorder and surface effects have been claimed to interpret structural and magnetic properties [2] of this type of materials.   The Fe-Mn-Cu system can be considered a good candidate for the occurrence of interesting magnetic behavior as spin glass-like and/or cluster superparamagnetism. Particularly, the study of the antiferromagnetic g-phase has attracted considerable attention due to its unusual magnetic behavior [3–5]. Recently, several authors have extensively studied the magnetism of mechanically prepared alloys Fe-Mn-Cu at the Cu-rich region of the phase diagram [3- 10]. Some results have been reported about the magnetic behavior of mechanically prepared Fe–Mn–Cu alloys at the Cu-rich region of the phase diagram [7- 10]. However at low Mn and Cu concentration, this ternary system is still few explored. Structural and hyperfine characterizations of mechanical milled (Fe79Mn21)0.70Cu0.30 alloys are presented. Samples (0.300g) were prepared by mechanical alloying from the elemental powders of Fe, Mn and Cu (99.99% purity), under Ar atmosphere. Ball milling was performed in a Retsch MM2 horizontal vibratory mill using 10 cm3 stainless steel vials and ball, with a sample to ball weight ratio of 1:10 at 33 Hz. All samples were milled during different times (1 - 15 h), with stops of 15 min each 45 min. The resulting powders were characterized by Mössbauer spectroscopy and X-ray diffraction.   X-ray diffraction and Mössbauer results indicate the formation of a random solid solution for milling times of 15 h and that the Cu addition favors the formation of a FCC phase with two different magnetic states at room temperature. For lower times, the presence of BCC phase is observed.   References: [1] Jartych E., J. of Mag. and Mag. Mat. 265 (2003) 176–188. [2] Greneche J. M., J. Non-Crystalline Solids 287 (2001) 37-44. [3] J. Restrepo, J.M. Grenèche, A. Hernando, P. Crespo, M.A. García, F.J. Palomares and J.M. González, J. Magn. Magn. Mat. 290-291, (2006) 602-605. [4] R. E. Vanderberghe, E. de Grave and P.M.A. de Bakker, Hyp. Interac. 83, (1994) 29-49. [5] C.L. Chien, S.H.Liou, D. Kofalt, W. Yu, T. Egami and T.R. McGuire, Phys. Rev. B 33, 5  (1986) 3247-3250. [6] F. Gauzzi, B. Verdini, G. Principi and B. Badan, J. Mater Sci. 18 (1983), 3661-3670. [7] V.V. Tcherdyntsev, L. Y. Pustov, S.D. Kaloshkin, E.V. Shelekhov, G. Principi, Hyp. Int. 168 (2006) 937-942. [8] S. J. Stewart, J. F. Marco, P. Crespo, J. J. Romero,  A. Martiìnez, A. Hernando, F. J. Palomares, J. M. Gonzalez, J. of nanoscience and nanotechnology 7(2007) 610-617. [9] J. Restrepo,_ J.M. Greneche, J.M. Gonzalez, Physica B 354 (2004) 174–182. [10] M.C. Alcocén, P. Crespo, A. Hernando and J. M. Gonzalez, J. Non-Crystalline Slolids 287 (2001) 268-271.