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15 Feb 2010

Volume 107, Issue 4, Articles (04xxxx)

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J. Appl. Phys. 107, 041101 (2010); http://dx.doi.org/10.1063/1.3318287 (13 pages)

Y. C. Tao and J. G. Hu
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back to top Dielectrics and Ferroelectricity

Surface and finite size effect on fluctuations dynamics in nanoparticles with long-range order

A. N. Morozovska and E. A. Eliseev

J. Appl. Phys. 107, 044101 (2010); http://dx.doi.org/10.1063/1.3291126 (6 pages) | Cited 1 time

Online Publication Date: 17 February 2010

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The influence of surface and finite size on the dynamics of the order parameter fluctuations and critical phenomena in the three-dimensional (3D)-confined systems with long-range order was not considered theoretically. In this paper, we study the influence of surface and finite size on the dynamics of the order parameter fluctuations in the particles of arbitrary shape. We consider concrete examples of the spherical and cylindrical ferroic nanoparticles within Landau–Ginzburg–Devonshire phenomenological approach. Allowing for the strong surface energy contribution in micro and nanoparticles, the analytical expressions derived for the Ornstein–Zernike correlator of the long-range order parameter spatial-temporal fluctuations, dynamic generalized susceptibility, relaxation times, and correlation radii discrete spectra are different from those known for bulk systems. Obtained analytical expressions for the correlation function of the order parameter spatial-temporal fluctuations in micro and nanosized systems can be useful for the quantitative analysis of the dynamical structural factors determined from magnetic resonance diffraction and scattering spectra. Besides the practical importance of the correlation function for the analysis of the experimental data, derived expressions for the fluctuations strength determine the fundamental limits of phenomenological theories applicability for 3D-confined systems.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.03.Cd Surface tension and related phenomena
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Dielectric characterization of NixCo1−xFe2O4 nanocrystals thin film over a broad frequency range (1 MHz–3 GHz)

Harun Bayrakdar and Kadir Esmer

J. Appl. Phys. 107, 044102 (2010); http://dx.doi.org/10.1063/1.3305333 (3 pages) | Cited 7 times

Online Publication Date: 25 February 2010

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We have theoretically and experimentally investigated the dielectric behavior of NixCo1−xFe2O4 nanoparticles (NPs) (where x = 0.0, 0.6, and 1.0), which have been synthesized by microwave induced combustion synthesis using urea as fuel. A variation of complex dielectric permittivity at room temperature with frequency in the range 1 MHz–3 GHz has been studied. The permittivity displays atomic polarization and electronic polarization. Particles showed phase purity and crystallinity in powder x-ray diffraction (XRD) analysis. At the same time, NixCo1−xFe2O4 NPs demonstrated a spinel cubic structure from XRD results.
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77.55.-g Dielectric thin films
81.07.Bc Nanocrystalline materials
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
75.50.Gg Ferrimagnetics
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
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