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Bhattacharjee A.,Visva Bharati University | Mandal H.,Visva Bharati University | Roy M.,Saha Institute of Nuclear Physics | Kusz J.,University of Silesia | Hofmeister W.,Institute For Geowissenschaften Der University
Journal of Magnetism and Magnetic Materials | Year: 2011

This paper reports on the physical nature of the fly ash sample of the Kolaghat Thermal Power Plant, India with an emphasis on its ultrafine nature. This paper also deals with the measurement of the magnetic properties of the fine particles of the fly ash sample. Particle sizes of this fly ash sample estimated from the SEM images lie within 0.165.50 μm, and the EDX spectral analysis indicates the presence of O, Al, Si, C, Fe, Mg, Na, K and Ti in this sample. From the XRD study, it is found that physical nature of conglomeration in the fly ash is crystalline and the major components are mullite (Al 6Si 2O 13) and quartz (SiO 2). Additionally, the presence of hematite, microcline, magnetite, maghemite and free iron in smaller fractions cannot be ruled out. A large magnetization observed at 5 K indicates the presence of magnetic components possibly due to superparamagnetism owing to very fine magnetic particles present. The hyperfine parameters obtained from the 57Fe Mössbauer spectroscopy, in general, support the observations made from the XRD analysis and in particular, provides the quantitative estimation of the different iron ions present in the sample. Precisely, this report presents experimental data on physical aspects of the fly ash sample of a thermal power plant which consists of coarse, fine and ultrafine magnetic particulate materials (PMs) and deals with an in-depth analysis of it. © 2011 Elsevier B.V. All rights reserved. Source


Bhattacharjee A.,Visva Bharati University | Roy D.,Visva Bharati University | Roy M.,Saha Institute of Nuclear Physics | Chakraborty S.,Saha Institute of Nuclear Physics | And 3 more authors.
Journal of Alloys and Compounds | Year: 2010

This paper presents the characteristics of iron oxides obtained through thermal degradation of a molecular ferrimagnet, {N(n-C4H 9)4[FeIIFeIII(C2O 4)3]}∞ and sheds light on the reaction pathways of degradation. The powder XRD pattern and the IR spectra of the degraded material reveal the formation of hematite. The SEM study exhibits that the degraded material consists of rod-like crystals of average length and diameter being 350 and 140 nm, respectively. But the mean crystallite size as estimated from the XRD pattern analysis is 169(2) nm. The magnetization study of the degraded material by SQUID shows the presence of Morin and Verwey transitions. Formation of ferrites through thermal degradation of the molecular magnetic precursor is further established by thermogravimetric study of the precursor. This is the first ever report of synthesis of nano-ferrites from a molecular magnet precursor, which underlines a new route for synthesis of ferrites. © 2010 Elsevier B.V. All rights reserved. Source


Oboz M.,University of Silesia | Talik E.,University of Silesia | Kusz J.,University of Silesia | Hofmeister W.,Institute For Geowissenschaften Der University
Journal of Alloys and Compounds | Year: 2010

Electronic structure, temperature dependences of the lattice parameters and magnetic properties of a crystal belonging to the series Gd7-xYxPd3 has been measured. Gd3Y4Pd3 orders ferromagnetically at 197 K and all measured physical properties show a strong anisotropy. The saturation magnetic moment per Gd ion is enhanced in relation to the theoretical value. The investigations of the magnetocaloric properties of the Gd3Y4Pd3 using the magnetization measurements have been performed in the temperature range of 2-300 K and magnetic field range of 0-7 T. The calculated values of entropy change ΔSm for examined compound amount -3.81 J/K kg for a axis and -3.97 for c axis at 7 T. © 2009 Elsevier B.V. All rights reserved. Source


Talik E.,University of Silesia | Klimczak M.,University of Silesia | Tran V.H.,Institute of Low Temperature And Structure Research | Kusz J.,University of Silesia | And 3 more authors.
Intermetallics | Year: 2010

Experimental results of the single-crystal X-ray diffraction, XPS, ac-magnetic susceptibility (ac-χ), dc-magnetization M(T), and electrical resistivity (ρ) measurements for the hexagonal Th7Fe3-type Gd5Y2Pd3 single crystal are presented. Anomalies in (ac-χ), (T) and M(T)-curves have allowed to establish that Gd5Y2Pd3 undergoes a long-range ferromagnetic-type ordering at TC = 263 K, followed by a spin-reorientation below 190 K. The magnetization data indicate that there is an excess of the magnetic moment for the Gd3+ ions. The observed XPS, magnetic and electrical resistivity behaviour points to the coexistence of localized magnetism from the magnetic Gd3+ ions and itinerant ferromagnetism from 4d- and 5d-electron bands. We discuss the magnetic behaviour of the Gd7-xYxPd3 solid solutions in terms of three competitive mechanisms: RKKY-interaction, magnetic frustration and spin-fluctuation. © 2009 Elsevier Ltd. All rights reserved. Source


Talik E.,University of Silesia | Oboz M.,University of Silesia | Tran V.H.,Institute of Low Temperature And Structure Research | Kusz J.,University of Silesia | And 2 more authors.
Journal of Crystal Growth | Year: 2010

Gd4Y3Pd3 belongs to Gd7-xYxPd3 series examined as prospective materials for magnetic refrigeration. Single crystal of Gd4Y3Pd3 was grown by the Czochralski method from a levitated melt. Investigations of X-ray diffraction, electronic structure, dc-magnetization M(T), ac-magnetic susceptibility (ac-χ) and electrical resistivity (ρ) for the hexagonal Th7Fe3-type for Gd4Y3Pd3 single crystal were performed. ac-χ(T) and M(T) measurements have allowed to establish that Gd4Y3Pd3 undergoes a long-range ferromagnetic ordering at TC=240 K, followed by a spin-reorientation below 160 K. The magnetization data indicate that there is an excess magnetic moment calculated per Gd3+ ions. The measured XPS valence band indicates the hybridization effect between Gd 5d, Y4d and Pd 4d states. The fitting of the XPS Y3d line and the powder X-ray diffraction spectrum shows the location of yttrium atoms in three nonequivalent gadolinium positions. Magnetic and electrical resistivity behaviour points to the coexistence of localized magnetism from the magnetic Gd3+ ions and itinerant ferromagnetism from 4d- and 5d-electron bands. The changes of magnetic frustration after yttrium substitution also influence the magnetic properties. © 2010 Elsevier B.V. All rights reserved. Source

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