Hcp cobalt nanocrystals with high magnetic anisotropy prepared by easy one-pot synthesis

Meziane, L.; Salzemann, Caroline; Aubert, Corinne; Gérard, Hélène; Petit, Christophe; Petit, Marc

doi:10.1039/c6nr05792f

Cited by 37 publications

(47 citation statements)

References 51 publications

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“…The estimated values of anisotropy constant for Co@A (fcc) and Co@C (hcp) phases are~28 × 10 4 J/m 3 and~39 × 10 4 J/ m 3 , respectively, which are in good agreement with the earlier reports [32,33]. The anisotropy constant for the Co@B (fcc and hcp) is~37 × 10 4 J/m 3 .…”

Section: Magnetic Measurementssupporting

confidence: 88%

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Manjunatha

Reddy

Mallikarjunaiah

et al. 2019

J Supercond Nov Magn

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It is well known that cobalt exhibits polymorphism, i.e., the co-existence of both the hcp and fcc phases. In particular, the method of synthesis and other thermodynamic conditions is known to play a crucial role in determining the particular phase of cobalt. In this work, we have compared the phase composition of the cobalt nanoparticles synthesized using two different solvents (water) and ethanol (Co@C). XRD measurements confirm the existence of fcc phase in commercial cobalt nanoparticles (Co@A), coexistence of fcc and hcp phases in Co@B, while the existence of the hcp phase in Co@C. We have studied these cobalt nanoparticles using 59 Co internal field nuclear magnetic resonance (IFNMR) for verification of phase composition. Our studies reveal that the Co@A has fcc as a major phase with minor quantity hcp phase. Co@B exhibits approximately equal amount of fcc and hcp phase while Co@C exhibits hcp as a major phase with minor fcc phase. Our SEM micrograph studies confirm that the cobalt particles have spherical shape in the fcc phase. The cobalt particles exhibit both spherical and dendrite morphology confirming the co-existence of fcc and hcp phases, while the sample with pure hcp phase exhibits the dendrite morphology. Our studies also throw light on understanding the effect of solvent in the phase formation of the cobalt nanoparticles.

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Section: Magnetic Measurementssupporting

confidence: 88%

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Manjunatha

Reddy

Mallikarjunaiah

et al. 2019

J Supercond Nov Magn

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“…Furthermore, we also find lattice distances between 0.18 nm and 0.21 nm, indicating the presence of pristine Co, which exhibits diffraction features in this range. 43 At room temperature and exposure to ambient air, it has been shown that hcp α-Co (hexagonal, P6 3 /mmc) is preferentially formed. 44 However, the fcc phase β-Co (cubic, Fm 3m) exhibits prominent features in this range as well (see Table S1 in the supplementary material).…”

Section: Resultsmentioning

confidence: 99%

Ultrashort XUV pulse absorption spectroscopy of partially oxidized cobalt nanoparticles

Schiffmann

Toulson

Knez

et al. 2020

Journal of Applied Physics

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High-order harmonic generation (HHG) based transient extreme ultraviolet (XUV) absorption spectroscopy is an emerging technique to trace photoinduced charge carrier dynamics in condensed phase materials with femtosecond and even attosecond temporal resolution and elemental specificity. However, its application to nanoparticulate samples that are relevant, for example, for novel photocatalytic light harvesting concepts, has been limited. This is in part due to the challenge to produce residual-free samples on ultrathin, XUV-transparent substrates as well as a widespread understanding that sparsely distributed nanoparticles do not provide sufficient contrast for XUV absorption measurements. Here, we present static XUV absorption spectra of partially oxidized Co nanowire-structures with diameters of approximately 4.5 nm and lengths between 10 and 40 nm, recorded with an ultrashort pulse HHG light source. Nanoparticles are synthesized by the agglomeration of Co atoms inside superfluid helium droplets, followed bysurfacedepositionandoxidationinambient air.Themethodisuniquely suited for residual-free synthesis of transition metal nanowires and their deposition on ultrathin substrates. Analysis by high-resolution transmission electron microscopy reveals the formation of CoO nanowires with regions of unoxidized Co in their interior. The nanoparticle samples are investigated in an HHGdriven ultrafast XUV absorption setup. Despite the low surface coverage of only 23%, the recorded spectrum exhibits a distinct absorption feature at the Co M 2,3 (2p) edge near 60 eV with a peak height of about 40 mOD. The results support the feasibility of table-top ultrafast transient XUV absorption studies of photoinduced dynamics in transition metal oxide nanoparticles with sub-monolayer surface coverage.

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“…25 Moreover, several publications relate the use of hcp Co NPs for magnetisation-based applications due to the requirement of small NPs with high anisotropy at usable temperatures, and hcp Co NPs of varying diameters have already been successfully synthesised. [90][91][92][93][94] As it has been shown that size-dependent effects are not prevalent in changes of the magnetic properties of Co clusters induced by ligand coatings, 41 only the influence of the density of the coating on the magnetisation of the 55-atom icosahedron and 57-atom hcp NPs was considered. Ten different coverages of three ligand functional groups commonly used for biocompatibility (-SH, -COOH, and -NH 2 ) were modelled on the icosahedral NP, increasing from 10% to a full 100% coverage in steps of 10%.…”

Section: Resultsmentioning

confidence: 99%

Effect of coverage on the magnetic properties of –COOH, –SH, and –NH₂ ligand-protected cobalt nanoparticles

Farkaš

Leeuw

2021

Nanoscale

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Hcp cobalt nanocrystals with high magnetic anisotropy prepared by easy one-pot synthesis

Cited by 37 publications

References 51 publications

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Ultrashort XUV pulse absorption spectroscopy of partially oxidized cobalt nanoparticles

Effect of coverage on the magnetic properties of –COOH, –SH, and –NH₂ ligand-protected cobalt nanoparticles

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Hcp cobalt nanocrystals with high magnetic anisotropy prepared by easy one-pot synthesis

Cited by 37 publications

References 51 publications

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

Ultrashort XUV pulse absorption spectroscopy of partially oxidized cobalt nanoparticles

Effect of coverage on the magnetic properties of –COOH, –SH, and –NH2 ligand-protected cobalt nanoparticles

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Effect of coverage on the magnetic properties of –COOH, –SH, and –NH₂ ligand-protected cobalt nanoparticles