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Temperature-dependent magnetization, anisotropy and conductivity of CoFe2-xSnxO4 (x = 0.025, 0.05, 0.075): Appearance of grain boundary conductivity at high temperatures
Kodam Ugendar
Published in Institute of Physics Publishing
2016
Volume: 49
   
Issue: 30
Abstract
The temperature dependence of magnetization, anisotropy, ac and dc conductivity of CoFe2-xSnxO4 (x = 0.025, 0.05, 0.075) were investigated and the results are reported. All the compounds were prepared by a solid-state reaction, and the formation of the compounds in the cubic inverse spinel phase was confirmed from their Rietveld refined x-ray diffraction (XRD) patterns and Raman spectra. Increments in the lattice constant were observed upon the partial substitution of Fe3+ by Sn4+. The presence of all elements and their ionic states were confirmed from x-ray photoelectron spectroscopic studies. Magnetic hysteresis loops were measured for each compound at temperature 20 K and 50-300 K (in steps of 50 K) using a superconducting quantum interference device vibrating sample magnetometer. Both magnetization and magnetic anisotropy showed a decrease in values with increasing Sn substitution. Room temperature (RT) magnetization is seen to decrease from 80-65.91 emu g-1 with increasing Sn concentration from x = 0 (CoFe2O4) to 0.075 (CoFe1.925Sn0.075O4). The high field regimes of the hysteresis loops were modeled using the law of approach to the saturation magnetization equation. The temperature variation of magnetization and magnetic anisotropy are explained on the basis of a one-ion model. Complex impedance spectroscopy studies at RT show that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of the grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. The RT total dc conductivity value of CoFe2-xSnxO4 (x = 0, 0.025, 0.05, 0.075) is found to be 5.78 × 10-8, 8.56 × 10-8, 1.44 × 10-7 and 1.11 × 10-7 S cm-1 respectively. The observation of well-distinguishable grain and grain boundary conductions and the low conductivity values in the CoFe2-xSnxO4 (x = 0, 0.025) materials indicates that these materials are promising candidates for high-frequency applications. © 2016 IOP Publishing Ltd.
About the journal
JournalJournal of Physics D: Applied Physics
PublisherInstitute of Physics Publishing
ISSN00223727
Open AccessNo
Concepts (25)
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    Ferrite
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    Grain boundaries
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    Hysteresis
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    Hysteresis loops
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    Iron compounds
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    Magnetic anisotropy
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    Magnetic materials
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    Magnetization
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    QUANTUM INTERFERENCE DEVICES
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    Solid state reactions
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    Spectroscopic analysis
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    Squids
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    Temperature distribution
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    Tin
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    X ray diffraction
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    X ray photoelectron spectroscopy
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    AC AND DC CONDUCTIVITIES
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    Ac conductivity
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    COMPLEX IMPEDANCE SPECTROSCOPY
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    GRAIN BOUNDARY CONDUCTIVITY
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    GRAIN-BOUNDARY CONDUCTIONS
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    High-frequency applications
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    TEMPERATURE-DEPENDENT MAGNETIZATIONS
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    Vibrating sample magnetometer
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    Saturation magnetization