Srikala, D. and Singh, V. N. and Mehta, B. R. and Patnaik, S. (2012) Signatures of spin-glass freezing in Co/CoO nanospheres and nanodiscs. Journal of Magnetism and Magnetic Materials, 324 (16). 2512-2518. ISSN 0304-8853

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Abstract

We present a study of the magnetic properties of Co nanoparticles having a combination of both spherical and disk shapes. The hcp Co nanospheres with an average diameter of 11 nm and nanodiscs of dimensions similar to 2.5 x 15 nm(2) were prepared by thermal decomposition of di-cobalt octacarbonyl in the presence of an amine surfactant. The as-synthesized nanoparticles were oxidized to grow an antiferromagnetic layer. High resolution transmission electron microscopy showed the presence of a ferromagnet/antiferromagnet (Co/Coo) interface with a 2.2-nm thick Coo shell on the spherical nanoparticles and 0.5 nm thick on nanodiscs. We report the temperature and field dependent DC magnetization, frequency, field, and temperature dependent AC susceptibility, and the radio frequency transverse susceptibility. A low temperature paramagnetic behavior was observed in the DC magnetization at high fields and is assigned to defects in the Coo shell that are not coupled to the antiferromagnetic lattice. Our results support the existence of a low temperature frozen, disordered magnetic state, characterized by a strong exchange coupling between the structurally disordered, spin-glass CoO shell and Co core.

Item Type:	Article
Additional Information:	copyright for this article belongs to M/s Elsevier
Subjects:	Materials Science Applied Physics/Condensed Matter
Divisions:	UNSPECIFIED
Depositing User:	Users 27 not found.
Date Deposited:	19 Aug 2026 11:02
Last Modified:	19 Aug 2026 11:02
URI:	https://npl.csircentral.net/id/eprint/3432

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