Hyperfine interactions on iron nuclei in the BCC and fractally decomposed BCC/FCC mixed phase iron–gold alloys

• Published in: Journal of alloys and compounds Vol. 458; no. 1; pp. 96 - 103
• Main Authors: Błachowski, A., Ruebenbauer, K., Przewoźnik, J., Żukrowski, J.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30.06.2008; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fractals; Impurities in metals; Iron binary alloys; Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.); Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetically ordered materials: other intrinsic properties; Mössbauer effect; other γ-ray spectroscopy; Mössbauer spectroscopy; Nanoparticles; Physics; Nanoparticles; Impurities in metals; Mössbauer spectroscopy; 75.50.Bb; Iron binary alloys; Fractals; 61.72.Ss; 61.43.Hv; 61.46.Df; 76.80.+y; Scanning electron microscopy; Moessbauer effect; Annealing; FCC lattices; Gold alloys; Paramagnetism; Spin density; Iron alloys; Magnetic transitions; 75.50.Bb; 61.72.Ss; 61.43.Hv; 61.46.Df; 76.80.+y; BCC lattices; Paramagnetic materials; Chemical composition; Ferromagnetism; Hyperfine interactions; Mossbauer spectroscopy; Iron binary alloys; Impurities in metals; Fractals; Nanoparticles
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2007.04.205

Iron–gold alloys for the gold concentration ranging from 1 at.% till 70 at.% were investigated by means of the 57Fe-14.4 keV Mössbauer spectroscopy, X-ray diffraction and scanning electron microscopy. Samples were prepared by arc melting of the elements, and investigated as cast and after annealing. A single BCC phase is obtained for the gold concentration up to about 3 at.%, while for the higher gold concentration one obtains mixed phase samples containing BCC and FCC phases both. The BCC phase is ferromagnetically ordered at room temperature. Contributions to the charge and spin density on iron atoms in the BCC phase due to the gold impurities were determined up to the second neighbors. The FCC phase is either magnetically ordered at room temperature or it is paramagnetic at the above temperature depending upon iron concentration, as the magnetic transition temperature is increasing with the increasing iron concentration. BCC/FCC mixed phase samples are characterized by very small crystallites (nanoparticles) of both phases. These nanoparticles form hierarchical fractal structures on the scale ranging from more than 1 mm till less than 30 nm.