Magnetic properties of cobalt and cobalt-platinum alloy nanoparticles synthesized via microemulsion technique

Kumbhar, Amar; Spînu, Leonard; Agnoli, F.; Wang, Kaiying; Zhou, Weilie; O’Connor, Charles J.

doi:10.1109/20.951128

Cited by 47 publications

(31 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Comparison with other synthetic preparations showed similar results, » 9 10 ±3 emu mg ±1 for CoPt particles grown from microemulsion techniques and 8 10 ±3 emu mg ±1 for reverse-micelle methods compared to the bulk CoPt value of 5 10 ±2 emu mg ±1 . [35,36] However, direct comparisons are not straightforward because the CP_Hsp and G41C_Hsp samples consist of mostly non-magnetic components, i.e., protein.…”

Section: Full Papermentioning

confidence: 99%

“…[14,36,37,42] However, synthesis of CoPt inside ferritin revealed no room temperature ferromagnetism before annealing. [14,36,37,42] Upon annealing, a coercive field of 300 G was observed, coupled with sintering of the particles that were up to 25 nm in diameter. [43] The MjHsp_CP system has the advantage of producing ferromagnetic materials under mild synthetic conditions.…”

Section: Full Papermentioning

confidence: 99%

“…These synthetic approaches include reducing metal-organic precursors with reductants such as borohydride and diols, [26,32,33] redox transmetallation reactions [34] using reverse micelles, [35] and microemulsion techniques. [36] Another promising approach is to use biomacromolecules as templates for directed fabrication of metallic nanophases. [1,3,17] This biomimetic approach has been exploited using the Fe-storage protein, ferritin, to grow CoPt nanoparticles that were subsequently annealed into the ordered L1 0 phase and templated into large 2D arrays.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Bio-inspired Synthesis of Protein-Encapsulated CoPt Nanoparticles

et al. 2005

View full text Add to dashboard Cite

Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bio-inspired Synthesis of Protein-Encapsulated CoPt Nanoparticles

et al. 2005

View full text Add to dashboard Cite

“…[24] We observe similarly poor characteristics for FePt nanoparticles synthesized using microemulsions with CTAB or 2-bis-ethyl-hexyl-sulfosuccinate likely due to low solubility of these ionic surfactants in iso-octane, and irreversible binding of the surfactant to the nanoparticles. In contrast, the relative inertness and high solubility of nonionic surfactants such as brij 56 or brij 52, used in the present study, provide a larger and tunable range of narrow dispersity water nanodroplets that can be used for nanoparticle synthesis.…”

mentioning

confidence: 91%

Synthesis and Assembly of Monodisperse High‐Coercivity Silica‐Capped FePt Nanomagnets of Tunable Size, Composition, and Thermal Stability from Microemulsions

et al. 2006

View full text Add to dashboard Cite

The large uniaxial magnetic anisotropy energy ) [1,2] of Fe-Pt alloys makes their nanostructured forms attractive for potential use as nanoscale magnetic bits in ultrahigh-density information storage devices [3][4][5][6][7] or as fillers to create new types of magnetocomposites. The high magnetic anisotropy and coercivity arise from the chemically ordered face-centered-tetragonal (fct) L1 0 phase, which is sensitive to both chemical composition and the size of the nanoparticles. [4,8,9] Control over particle size and dispersity [10][11][12][13] is essential to form ordered arrays of nanoparticles, and preserve these features against agglomeration [14,15] during high-temperature annealing (e.g., 550°C) treatments used to obtain the L1 0 phase. Therefore, it is crucial to develop protocols to produce FePt nanoparticles with control over composition, particle size, and dispersity, and thermal stability for exploiting their assemblies for data-storage media applications. The synthesis technique described here is a promising approach to realize all these features simultaneously.Prior works have demonstrated FePt nanoparticles synthesis with either excellent size control [3][4][5]10,16] or chemical compositional control [17][18][19] but not both. Thermal decomposition of Fe(CO) 5 vapor, and reduction of Pt(acac) 2 , produces monodisperse nanoparticles with tunable sizes in the 2-15 nm range. [3][4][5]20] But, the chemical composition of the nanoparticle is different from the initial molar ratio of the metal precursors due to different precursor decomposition rates.[10] Size control is further complicated by the strong influence of parameters such as Ar gas flow rate, heating rate, and temperature.[ [19] of the initial molar ratio of the metal precursors, but the particle size is constrained to a limited range of approximately 3-5 nm. Neither of these two synthesis routes is easily amenable to coating the nanoparticles with a protective shell of a thermally stable material (e.g., silica or titania) that could prevent particle shape and size changes during postsynthesis annealing for obtaining the L1 0 phase. Although a Fe 3 O 4 shell can be formed [15] by the thermal decomposition method, the shell degrades at temperatures less than 600°C and destroys the nanoparticle structure and shape. Techniques to coat a silica shell on clusters of magnetic nanoparticles that have been presynthesized using a separate processing method have been demonstrated, [21][22][23] but these techniques are not well suited for creating organized assemblies of well-separated nanoparticles for recording media applications. Here, we report the room-temperature synthesis of monodisperse FePt nanoparticles with tunable particle size over an extended range of 4-20 nm and excellent compositional control using microemulsions. We further use the same microemulsion to enhance the nanoparticle thermal stability by forming a 2 nm thick silica shell, which is also used for functionalization with organosilanes. Organized assemblies formed from the molecul...

show abstract

“…4,8 However, little work has been done on soft chemistry processes for the fabrication of such ferromagnetic nanocrystals 24 and there are only few reports on soft chemistry synthesis of nanoalloys such as CoPt. [25][26][27] Usually, the high temperature decomposition of organo-metallic compounds is used to form such nanoalloys. 6,28 -31 In this article, we investigate by magneto-optical Kerr effect ͑MOKE͒, the magnetic properties of various organizations of colloidal cobalt and CoPt nanoparticles deposited on highly ordered pyrolytic graphite ͑HOPG͒ substrates.…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of cobalt and cobalt–platinum nanocrystals investigated by magneto-optical Kerr effect

Petit

Rusponi

Brune

2004

Journal of Applied Physics

View full text Add to dashboard Cite

Magneto-optical Kerr effect, is used to investigate the magnetization of film made of uncoalesced cobalt and cobalt-platinum nanocrystals. For the pure cobalt nanocrystals, different film morphologies are obtained through application of magnetic field during deposition. These morphologies have quite different magnetic properties, which is rationalized by considering dipolar interactions and the associated demagnetizing factor. We show that fast annealing can be used to trigger changes in the particles' crystalline structure while largely avoiding their coalescence. With increasing the annealing temperature, 2.7 nm CoPt nanocrystals show a transition from the magnetically soft face-centered-cubic phase to the hard face-centered-tetragonal L1 0 phase. In particular fast annealing to 950 K is shown to produce largely uncoalesced nanocrystals ferromagnetic at room temperature. With 7 nm cobalt nanocrystals, fast annealing at 500 K equally results in ferromagnetism at room temperature without inducing coalescence between the nanocrystals in the film.

show abstract

Magnetic properties of cobalt and cobalt-platinum alloy nanoparticles synthesized via microemulsion technique

Cited by 47 publications

References 9 publications

Bio-inspired Synthesis of Protein-Encapsulated CoPt Nanoparticles

Bio-inspired Synthesis of Protein-Encapsulated CoPt Nanoparticles

Synthesis and Assembly of Monodisperse High‐Coercivity Silica‐Capped FePt Nanomagnets of Tunable Size, Composition, and Thermal Stability from Microemulsions

Magnetic properties of cobalt and cobalt–platinum nanocrystals investigated by magneto-optical Kerr effect

Contact Info

Product

Resources

About