Enhanced magnetization of nanoscale colloidal cobalt particles

Chen, J. P.; Sorensen, C. M.; Klabunde, Kenneth J.; Hadjipanayis, G. C.

doi:10.1103/physrevb.51.11527

Cited by 298 publications

(212 citation statements)

References 24 publications

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“…For bulk fcc Co, the effective magnetocrystalline anisotropy constant is given by K eff =K 1 /4, 30,41 where K 1 is the first-order anisotropy constant whose value is approximately K 1 Ϸ 2.6ϫ 10 6 erg/ cm 3 for Co. 42,43 This leads to K eff Ϸ 6.5 ϫ 10 5 erg/ cm 3 . In comparison to this value, our values of K are larger, strongly suggesting that surface anisotropy gives an additional contribution for such small particles and raises the total effective anisotropy.…”

Section: B Magnetizationmentioning

confidence: 99%

Tunneling magnetoresistance inCo−ZrO2granular thin films

et al. 2006

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Granular films composed of well defined nanometric Co particles embedded in an insulating ZrO 2 matrix were prepared by pulsed laser depositon in a wide range of Co volume concentrations ͑0.15Ͻ x Ͻ 0.43͒. High-resolution transmission electron microscopy ͑TEM͒ showed very sharp interfaces between the crystalline particles and the amorphous matrix. Narrow particle size distributions were determined from TEM and by fitting the low-field magnetic susceptibility and isothermal magnetization in the paramagnetic regime to a distribution of Langevin functions. The magnetic particle size varies little for Co volume concentrations x Ͻ 0.32 and increases as the percolation limit is approached. The tunneling magnetoresistance ͑TMR͒ was successfully reproduced using the Inoue-Maekawa model. The maximum value of TMR was temperatureindependent within 50-300 K, and largely increased at low T, suggesting the occurrence of higher-order tunneling processes. Consequently, the tunneling conductance and TMR in clean granular metals are dominated by the Coulomb gap and the inherent particle size distribution.

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Section: B Magnetizationmentioning

confidence: 99%

Tunneling magnetoresistance inCo−ZrO2granular thin films

et al. 2006

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“…In addition, the net anisotropy of the particle exceeds the bulk value. 8,9 This excess was recently correlated to the augmentation of the orbital magnetic moment of the peripheral atoms. 10,11 Magnetic nanoparticles are also good candidates for the study of quantum effects in intermediate scales between the microscopic and the macroscopic classical world.…”

Section: Introductionmentioning

confidence: 96%

Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: Influence of the surface and of interparticle interactions

et al. 2002

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We study the magnetic properties of spherical Co clusters with diameters between 0.8 nm and 5.4 nm (25 to 7500 atoms) prepared by sequential sputtering of Co and Al2O3. The particle size distribution has been determined from the equilibrium susceptibility and magnetization data and it is compared to previous structural characterizations. The distribution of activation energies was independently obtained from a scaling plot of the ac susceptibility. Combining these two distributions we have accurately determined the effective anisotropy constant K ef f . We find that K ef f is enhanced with respect to the bulk value and that it is dominated by a strong anisotropy induced at the surface of the clusters. Interactions between the magnetic moments of adjacent layers are shown to increase the effective activation energy barrier for the reversal of the magnetic moments. Finally, this reversal is shown to proceed classically down to the lowest temperature investigated (1.8 K).

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“…Research on nanoparticles has gathered wide attention during the last decade because of their unusual and size-dependent optical [1], magnetic [2] and [3], electronic [4] and [5], and chemical [6] and [7] properties. To fully utilize these properties, the size and shape must be well controlled.…”

Section: Introductionmentioning

confidence: 99%

Influence of ligand structure on the stability and oxidation of copper nanoparticles

Kanninen¹,

Johans²,

Merta

et al. 2008

Journal of Colloid and Interface Science

239

170

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The stability and oxidation of copper nanoparticles stabilized with various ligands have been studied. Lauric acid-capped copper nanoparticles were prepared by a modified Brust-Schiffrin method. Then, ligand exchange with an excess of different capping agents was performed.Oxidation and stability were studied by UV-vis, XRD, and TEM. Alkanethiols and oleic acid were found to improve air stability. The oxidation resistance of thiol-capped copper nanoparticles was found to increase with the chain length of the thiol. However, excess thiol caused etching of the particles under nitrogen. With oleic acid no etching was observed under nitrogen. After oxidation, no traces of the ligand-exchanged particles were found, suggesting their dissolution due to excess ligand. Oleic acid protected the particles against oxidation better than the tested thiols at large excess (ligand-copper ratio 20:1).

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Enhanced magnetization of nanoscale colloidal cobalt particles

Cited by 298 publications

References 24 publications

Tunneling magnetoresistance inCo−ZrO2granular thin films

Tunneling magnetoresistance inCo−ZrO2granular thin films

Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: Influence of the surface and of interparticle interactions

Influence of ligand structure on the stability and oxidation of copper nanoparticles

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