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Journal ArticleDOI

Structural and Magnetic Properties of CoFe2O4 and Co0.5Zn0.5Fe2O4 Nanoparticles for the Magnetoelectric Composite Films

16 Dec 2011-Integrated Ferroelectrics (Taylor & Francis Group)-Vol. 131, Iss: 1, pp 102-109
TL;DR: In this paper, cobalt ferrite and Zn-doped CoFe2O4 nanoparticles were synthesized using a low temperature solution method, which showed promising results for use in magnetoelectric composite films.
Abstract: In the present work, cobalt ferrite and Zn-doped cobalt ferrite nanoparticles were synthesized using a low temperature solution method. A study of the magnetic properties of the CoFe2O4 nanoparticles shows high coercivity at 10 K. Co0.5Zn0.5Fe2O4 nanoparticles show a lower coercive field but a higher saturation magnetization as compared to CoFe2O4 nanoparticles. Blocking temperature of the particles decreased from 355 K for CoFe2O4 to 220 K for Co0.5Zn0.5Fe2O4. A PbZr0.52Ti0.48O3:CoFe2O4 composite film prepared using CoFe2O4 nanoparticles dispersed in PbZr0.52Ti0.48O3 solution shows ferroelectric and ferromagnetic properties. Such low-cost synthesis approach shows promise for use in magnetoelectric composite films.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a structure property correlation has been established by proposing a cation distribution, which enables to explain the enhancement of magnetic properties of nanocrystalline cobalt ferrite nanoparticles.

68 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present electric and ME properties of 3-0 type nanocomposite thin films with various concentrations of CoFe2O4 NPs dispersed in PbZr0.52Ti0.48O3 (PZT) matrix.
Abstract: Magnetoelectric (ME) coupling (αE) in piezoelectric:magnetostrictive composites is mediated through mechanical strain at their interfaces. Incorporating magnetic nanoparticles (NPs) in piezoelectric matrix enhances interfacial area between the two phases and therefore large αE can be expected. Here, we present electric and ME properties of 3-0 type nanocomposite thin films with various concentrations of CoFe2O4 NPs dispersed in PbZr0.52Ti0.48O3 (PZT) matrix. Nanocomposite films show only a slight reduction in remnant electric-polarization as compared to that of PZT. A nanocomposite film with 0.1% CoFe2O4 (molar concentration) exhibited the highest transverse αE of 549 mV/cmOe at 453 Oe dc bias and 1 kHz.

41 citations

Journal ArticleDOI
TL;DR: In this article, the properties of nanoferrites were investigated by X-ray diffraction, 57 Fe Mossbauer spectroscopy and magnetometry, and the evolution of the properties has been explained on the basis of Mg content and crystallite sizes.

28 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis and process conditions helpful in obtaining easily sinterable CoFe2O4 nanoparticles with coercive magnetic flux density (Hc) in the range 5.5-31.9 kA/m and Ms in range 47.9-84.9 A·m2Kg-1.
Abstract: Cobalt ferrite (CoFe2O4) is an engineering material which is used for applications such as magnetic cores, magnetic switches, hyperthermia based tumor treatment, and as contrast agents for magnetic resonance imaging. Utility of ferrites nanoparticles hinges on its size, dispersibility in solutions, and synthetic control over its coercivity. In this work, we establish correlations between room temperature co-precipitation conditions, and these crucial materials parameters. Furthermore, post-synthesis annealing conditions are correlated with morphology, changes in crystal structure and magnetic properties. We disclose the synthesis and process conditions helpful in obtaining easily sinterable CoFe2O4 nanoparticles with coercive magnetic flux density (Hc) in the range 5.5-31.9 kA/m and Ms in the range 47.9-84.9 A·m2Kg-1. At a grain size of ~ 54±2 nm (corresponding to 1073 K sintering temperature), multi-domain behavior sets in, which is indicated by a decrease in Hc. In addition, we observe an increase in lattice constant with respect to grain size, which is the inverse of what is expected of in ferrites. Our results suggest that oxygen deficiency plays a crucial role in explaining this inverse trend. We expect the method disclosed here to be a viable and scalable alternative to thermal decomposition based CoFe2O4 synthesis. The magnetic trends reported will aid in the optimization of functional CoFe2O4 nanoparticles.

20 citations


Cites background from "Structural and Magnetic Properties ..."

  • ...There are several on-going efforts in this direction to enhance device functionality of this nanomaterial by improving its coercivity and saturation magnetization [7], [8]....

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Journal ArticleDOI
TL;DR: In this article, the surface layer effects on the dc and ac magnetic measurements of oleic-acid coated CoFe2O4 nanoparticles were studied and a spinglass correction term to account for a magnetically disordered surface layer was found to accurately describe the temperature dependence of the saturation magnetization.
Abstract: In the present work, we have studied the surface layer effects on the dc and ac magnetic measurements of oleic-acid coated CoFe2O4 nanoparticles The blocking temperature for the nanoparticles is found to be 278 K with 100 Oe field and above this temperature, the nanoparticles show superparamagnetic behavior A spin-glass correction term to the Bloch law (to account for a magnetically disordered surface layer) was found to accurately describe the temperature dependence of the saturation magnetization By studying the frequency dependence of the ac magnetization, the coated nanoparticles were shown to have moderate particle interaction strength with anisotropy energy and anisotropy constant of 160 meV and 223 × 105 erg/cm3, respectively A feature in the ac magnetization at 53 K was confirmed to be the result of surface spin-glass freezing on the individual particles Because of decreased interaction strength due to the oleic acid coating, the presence of a magnetically disordered surface layer due to sup

15 citations

References
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Journal ArticleDOI
TL;DR: In this article, a review of mostly recent activities can be found, with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972.
Abstract: Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

3,288 citations

Journal ArticleDOI
TL;DR: In this paper, magnetic nanoparticles of cobalt ferrite have been synthesized by wet chemical method using stable ferric and cobalt salts with oleic acid as the surfactant.

784 citations


"Structural and Magnetic Properties ..." refers background in this paper

  • ...The value of TB depends on composition, applied magnetic field, time scale of measurement, and particle size [19, 20]....

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  • ...As shown in the literature, a decrease in blocking temperature may correspond to a decrease in particle size [20] or doping of the Co site [11]....

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Journal ArticleDOI
TL;DR: By combining nonhydrolytic reaction with seed-mediated growth, high-quality and monodisperse spinel cobalt ferrite, CoFe(2)O(4), nanocry crystals can be synthesized with a highly controllable shape of nearly spherical or almost perfectly cubic, which possesses tremendous potentials in fundamental understanding of magnetism and in technological applications of magnetic nanocrystals for high-density information storage.
Abstract: By combining nonhydrolytic reaction with seed-mediated growth, high-quality and monodisperse spinel cobalt ferrite, CoFe2O4, nanocrystals can be synthesized with a highly controllable shape of near...

776 citations

Journal ArticleDOI
TL;DR: In this paper, the coercive force and remanence of essentially spherical iron and iron-cobalt alloy particles with diameters from 20 to 3000 A have been measured at 4°, 76°, and 207°K and compared to the theoretically predicted behavior.
Abstract: The coercive force and remanence of essentially spherical iron and iron‐cobalt alloy particles with diameters from 20 to 3000 A have been measured at 4°, 76°, and 207°K and compared to the theoretically predicted behavior. The remanence shows a broad, plateau‐like maximum while the coercive force has a rather sharp maximum. The maximum of the coercive force occurs at a much larger particle diameter than the maximum of the remanence. It is shown that these essential characteristics follow from the theory. Deviations from theory are seen in the smaller size range and can be accounted for by the distribution of particle sizes. A general treatment of the coercive force of mixtures of thermally stable, high coercive force particles with superparamagnetic and multidomain particles is given.

550 citations