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    Spin-flop transition, magnetic and microwave absorption properties of alpha-Fe2O4 spinel type ferrite nanoparticles
    (ELSEVIER SCIENCE BV, 2013) Yalcin, Orhan; Bayrakdar, Harun; Ozum, Songul
    We have prepared NiFe2O4, CoFe2O4, Ni0.6Zn0.4Fe2O4 and ZnFe2O4 spinel type ferrite nanoparticles by surfactant-assisted hydrothermal process using cetyltrimethylammonium bromide (CTAB). The spin-flop transition, magnetic, dielectric and permittivity characterizations have been investigated. The spin-flop transition occurs from antiferromagnetic state to mixed state and then ferromagnetic state for Zn doped samples. The spin-flop transition occurs in the temperature range of 50-250 K. The ionic conduction, dipolar relaxation, atomic polarization and electronic polarization are the main mechanisms that contribute to the permittivity of a dielectric material. The permittivity increases with increasing frequency. This suggests a resonance behavior, which is expected when the ferrite samples are highly conductive and skin effect become significant. These samples will provide great benefits for electromagnetic applications and electromagnetic interference shielding characteristics. (C) 2013 Elsevier B.V. All rights reserved.
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    Synthesis and investigation of small g-values for smart spinel ferrite nanoparticles
    (Elsevier Science Sa, 2021) Bayrakdar, Harun; Yalcin, Orhan; Ozum, Songul; Cengiz, Ugur
    Smart spinel and hexagonal ferrite nanoparticles (NPs) have been fabricated by ethylenediaminetetraacetic acid (EDTA) and cetyltrimethylammonium bromide (CTAB) assisted hydrothermal route by using NaOH solution. Electron spin resonance (ESR) measurements of the spinel and hexagonal ferrite NPs have been performed by a high sensitive conventional x.band (similar to 9.5-9.8 GHz) spectrometer at room temperature (RT). The measured five small g-values by ESR spectra at RT may be relevant for quantum information processing. Quantum computing and relativistic quantum computing by two-level system (qubit) have been realized by spinel type NPs at RT. Temperature evolution of magnetic hysteresis loops, magnetization, coercivity (H-C), saturation field (H-S), saturation magnetization (M-S) and remanent magnetization (M-r) have been investigated. (C) 2021 Elsevier B.V. All rights reserved.