Structure and magnetism of well defined cobalt nanoparticles embedded in a niobium matrix

Jamet, M.; Dupuis, V.; Mélinon, P.; Guiraud, Germain; Pérez, A.; Wernsdorfer, Wolfgang; Traverse, A.; Baguenard, B.

doi:10.1103/physrevb.62.493

Cited by 91 publications

(77 citation statements)

References 29 publications

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“…However, it is well known that the bulk value is an overestimation of the particle magnetization in fine particle systems, due to strong surface and finite-size effects. 34,35 In our case, around 50-60 % of Co atoms are affected by the lowcoordination number at the surface, giving rise to smaller M S as compared to bulk Co. Consequently, this method leads to an underestimation of the average particle size 34,35 as compared to that obtained from TEM.…”

Section: A DC Susceptibilitymentioning

confidence: 74%

“…Luis et al 40 recently reported a size-dependent effective anisotropy constant of sputtered Co cluster in Al 2 O 3 that went down from 2.4ϫ 10 7 erg/ cm 3 for ͗D͘ = 0.8 nm to 3 ϫ 10 5 erg/ cm 3 for ͗D͘ = 5.2 nm and showed a linear dependence on the logarithm of the mean diameter. Jamet et al 34 report a slightly smaller effective anisotropy constant of 2 ϫ 10 6 erg/ cm 3 for Co particles with a 3-nm diameter in a niobium matrix. Our results are in good agreement with these experimental findings.…”

Section: B Magnetizationmentioning

confidence: 99%

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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: A DC Susceptibilitymentioning

confidence: 74%

Section: B Magnetizationmentioning

confidence: 99%

Tunneling magnetoresistance inCo−ZrO2granular thin films

et al. 2006

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“…Indeed, previous structural studies 11,5 showed that one (resp. two) cobalt atomic layer diffuses inside the Pt (resp.…”

Section: Discussionmentioning

confidence: 99%

“…Note that Co/Nb multilayers are also used in superconducting spin valve devices 4 . For these reasons, a detailed study of Co clusters embedded in a superconducting niobium matrix is reported in a previous paper 5 . Though cobalt clusters have similar structures in Co/Pt and Co/Nb systems (a pure cobalt core and an alloyed interface), we observe that their magnetic properties are drastically different.…”

Section: Introductionmentioning

confidence: 99%

Interface magnetic anisotropy in cobalt clusters embedded in a platinum matrix

Jamet¹,

Négrier²,

Dupuis³

et al. 2001

Journal of Magnetism and Magnetic Materials

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A low concentration of cobalt clusters with a fcc structure and containing almost one thousand atoms are embedded in two different metallic matrices: platinum and niobium. Samples have been prepared using a co-deposition technique. Cobalt clusters preformed in the gas phase and matrix atoms are simultaneously deposited on a silicon substrate under Ultra High Vacuum (UHV) conditions. This original technique allows to prepare nanostructured systems from miscible elements such as Co/Pt and Co/Nb in which clusters keep a pure cobalt core surrounded with an alloyed interface. Magnetic measurements performed using a Vibrating Sample Magnetometer (VSM) reveal large differences in the magnetic properties of cobalt clusters in Pt and Nb pointing out the key role of cluster/matrix interfaces.

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“…Atomic structure in nanoparticles can be changed pseudoepitaxially by embedding them in a matrix of a different material, thereby potentially offering a degree of control over their magnetism. Atomic structure change has been reported in Fe and Co nanoparticles embedded in various matrices [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. A convenient way of embedding nanoparticles in a matrix, directly from the gas phase, is provided by the low energy cluster beam deposition (LECBD) method [22].…”

Section: Introductionmentioning

confidence: 99%

Structure and magnetism in Cr-embedded Co nanoparticles

Baker¹,

Kurt²,

Roy³

et al. 2016

J. Phys.: Condens. Matter

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We present the results of an investigation into the atomic structure and magnetism of 2 nm diameter Co nanoparticles embedded in an antiferromagnetic Cr matrix. The nanocomposite films used in this study were prepared by co-deposition directly from the gas phase, using a gas aggregation source for the Co nanoparticles and a molecular beam epitaxy (MBE) source for the Cr matrix material. Co K and Cr K edge extended x-ray absorption fine structure (EXAFS) experiments were performed in order to investigate atomic structure in the embedded nanoparticles and matrix respectively, while magnetism was investigated by means of a vibrating sample magnetometer. The atomic structure type of the Co nanoparticles is the same as that of the Cr matrix (b.c.c.) although with a degree of disorder. The net Co moment per atom in the Co/Cr nanocomposite films is significantly reduced from the value for bulk Co, and decreases as the proportion of Co nanoparticles in the film is decreased; for the sample with the most dilute concentration of Co nanoparticles (4.9% by volume), the net Co moment was 0.25   /atom. After field cooling to below 30 K all samples showed an exchange bias, which was largest for the most dilute sample. Both the structural and magnetic results point towards a degree of alloying at the nanoparticle/matrix interface, leading to a core/shell structure in the embedded nanoparticles consisting of an antiferromagnetic CoCr alloy shell surrounding a reduced ferromagnetic Co core.

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Structure and magnetism of well defined cobalt nanoparticles embedded in a niobium matrix

Cited by 91 publications

References 29 publications

Tunneling magnetoresistance inCo−ZrO2granular thin films

Tunneling magnetoresistance inCo−ZrO2granular thin films

Interface magnetic anisotropy in cobalt clusters embedded in a platinum matrix

Structure and magnetism in Cr-embedded Co nanoparticles

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