Magnetic properties of superparamagnetic, nanocrystalline cobalt ferrite thin films deposited at low temperature

Sangeneni, Neelima and Taddei, KM and Bhat, Navakanta and Shivashankar, SA (2018) Magnetic properties of superparamagnetic, nanocrystalline cobalt ferrite thin films deposited at low temperature. In: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 465 . pp. 590-597.

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Abstract

Bulk cobalt ferrite, being a hard ferrite, shows high magnetization, high resistivity and high coercivity. If thin films of cobalt ferrite can be deposited at a low enough temperature and if its coercivity can be reduced, cobalt ferrite will make a very good candidate for use as a magnetic core of an integrated inductor in RF-CMOS ICs. Though polycrystalline and epitaxial thin films of cobalt ferrite have been made by various techniques, there are no reports of thin films of superparamagnetic cobalt ferrite. In this work, nanocrystalline cobalt ferrite thin films, which are superparamagnetic as deposited, have been prepared in the solution medium at similar to 190 degrees C, using microwave irradiation. The as-prepared films have a saturation magnetization (MS) of 401 emu/cc and coercivity (H-C) of 19 Oe at room temperature for a crystallite size of 2 nm. The cobalt ferrite powder obtained as a byproduct during the same process has M-S of 50 emu/g and H-C of 5 Oe at room temperature, making it superparamagnetic. The as-prepared films were annealed in air at 300 degrees C for 5 min and 10 min. Annealing for 10 min results in an increase in crystallite size to 36 nm, MS increases from 401 emu/cc to 545 emu/cc, and H-C increases from 19 Oe to 860 Oe. The change in magnetic properties can be directly associated with change in the crystallite size and degree of crystallographic inversion, as determined by neutron diffraction and deduced from X-ray photoelectron spectroscopy.

Item Type:	Journal Article
Publication:	JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copy right for this article belong to ELSEVIER SCIENCE BV
Keywords:	Cobalt ferrite; Ferrite thin films; Magnetic materials; Superparamagnetism
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	22 Oct 2018 15:03
Last Modified:	22 Oct 2018 15:03
URI:	http://eprints.iisc.ac.in/id/eprint/60922

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