https://doi.org/10.1140/epjd/e2003-00113-x
Matrix embedded cobalt-carbon nano-cluster magnets: behavior as room temperature single domain magnets
Institute for Molecular Science, Nishigo-naka 38, Myodaiji, Okazaki 444-8585, Japan
Corresponding author: a nishi@ims.ac.jp
Received:
10
September
2002
Published online:
3
July
2003
A new type of Co-C nanoparticles is synthesized from CH2Cl2 solution of
Co4(CO)12 by heating up to 210 °C in a closed vessel.
Transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS)
observation show that the particles are embedded in amorphous carbon and their average
size is 12 nm. The radial structure function obtained from the extended X-ray absorption
fine structure (EXAFS) of the Co K-edge absorption of the Co-C nanoparticles provides a
Co-C average distance of 2.08 Å and the Co-Co distances of 3.18 Å and 3.9 (
) Å. The particles exhibit the magnetic hysteresis curve with a coercive force of 200 Oe
at 20 K and 260 Oe at 300 K. The temperature dependence of the magnetic susceptibility
measured under zero-field cooling and 10 Oe field cooling conditions exhibits the behavior
characteristic of a set of single magnetic domain nanomagnets in an amorphous carbon matrix.
PACS: 36.40.-c – Atomic and molecular clusters / 36.40.Cg – Electronic and magnetic properties of clusters / 36.40.Mr – Spectroscopy and geometrical structure of clusters / 75.50.Tt – Fine-particle systems; nanocrystalline materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003
