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Magnetic properties of annealed core-shell CoPt nanoparticles

Title
Magnetic properties of annealed core-shell CoPt nanoparticles
Authors
Bigot J.-Y.Kesserwan H.Halte V.Ersen O.Moldovan M.S.Kim T.H.Jang J.-T.Cheon J.
Ewha Authors
김태희
SCOPUS Author ID
김태희scopus
Issue Date
2012
Journal Title
Nano Letters
ISSN
1530-6984JCR Link
Citation
vol. 12, no. 3, pp. 1189 - 1197
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
A precise control and understanding of the magnetization dynamics of nanostructures is an important topic in applied nanosciences. Herein, we perform such control by annealing crystalline (Co/core)-(Pt/shell) nanoparticles. Using electron tomography, temperature dependent electron microscopy and time-resolved magneto-optics, we establish a clear correlation between the magnetization dynamics and the crystalline structure of the nanoparticles. For a mild laser annealing (370 K) the Co-Pt nanoparticles keep their core-shell structure and remain superparamagnetic with a blocking temperature T B = 66 K. Their time-resolved reflectivity shows that they are locally organized into a supra-crystalline ordered layer in the region of the laser spot. In contrast, a thermal annealing at higher temperatures (up to 700 K) modifies the structure of the individual nanoparticles into a CoPt crystalline ferromagnetic phase, with T B,anneal = 347 K. Correspondingly, the magneto-crystalline anisotropy of the annealed CoPt nanoparticles increases and their magnetization dynamics displays a motion of precession, characteristic of ferromagnetic nanostructures and which is absent in the superparamagnetic Co-Pt core-shells. © 2012 American Chemical Society.
DOI
10.1021/nl300306a
Appears in Collections:
자연과학대학 > 물리학전공 > Journal papers
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