Magnetic properties of iron nitride-alumina nanocomposite materials prepared by high-energy ball milling

• Published in: The European physical journal. D, Atomic, molecular and optical physics (Print) Vol. 24; no. 1-3; pp. 93 - 96
• Main Authors: MISHRA, S. R, LONG, G. J, GRANDJEAN, F, HERMANN, R. P, ROY, S, ALI, N, VIANO, A
• Format: Conference Proceeding Journal Article Web Resource
• Language: English
• Published: Les Ulis Springer 01.06.2003; Bologna Società italiana di fisica; Berlin EDP sciences; Springer Science & Business Media B.V
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Diamagnetism and paramagnetism; Diamagnetism, paramagnetism and superparamagnetism; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Mossbauer effect; other γ-ray spectroscopy; Mössbauer effect; other γ-ray spectroscopy; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; Grain boundaries; Hyperfine magnetic field; Particle size; Moessbauer effect; Inorganic compounds; Magnetization; Ball mill; Transition element compounds; Isomer shift; Superparamagnetism; XRD; Experimental study; Powder metallurgy; Iron nitrides; Magnetic particles; Field distribution; Composite materials; Coercive force; Nanocomposite; Electron density; Aluminium oxides
• ISSN: 1434-6060; 1434-6079
• DOI: 10.1140/epjd/e2003-00146-1

The structural and magnetic properties of the granular iron nitride-alumina composite materials: (FexN)(0.2)(Al2O3)(0.8) and (FexN)(0.6)(Al2O3)(0.4), fabricated using high-energy ball milling have been determined by using X-ray diffraction, Mossbauer spectroscopy, and magnetization measurements. The Mossbauer spectra, fit with a distribution of hyperfine fields between zero and 40 T. indicate that the weighted average field decreases with increasing milling time. The isomer shift increases with milling time because of a reduced iron 4s-electron density at the grain boundaries. Coercive fields as high as 325 and 110 Oe are obtained for (FexN)(0.2)(Al2O3)(0.8) at 5 and 300 K, respectively; the increase in the coercive field upon cooling indicates the presence of superparamagnetic particles. The coercive field increases with milling time because of the reduced particle size. The decrease in the magnetization results from the increase in both the superparamagnetic fraction and the concentration of surface defects with increased milling time.