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Effect of annealing on the magnetic properties of ball milled NiO powders

Kisan, Bhagban; Saravanan, P.; Layek, Samar; Verma, H. C.; Hesp, David; Dhanak, Vinod; Krishnamurthy, Satheesh and Perumal, A. (2015). Effect of annealing on the magnetic properties of ball milled NiO powders. Journal of Magnetism and Magnetic Materials, 384 pp. 296–301.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1016/j.jmmm.2015.02.065
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Abstract

We report systematic investigations on structural and magnetic properties of nanosized NiO powders prepared by the ball milling process followed by systematic annealing at different temperatures. Both as-milled and annealed NiO powders exhibit face centered cubic structure, but average crystallite size decreases (increases) with increasing milling time (annealing temperature). Pure NiO exhibits antiferromagnetic nature, which transforms into ferromagnetic one with moderate moment at room temperature with decreasing crystallite size. The on-set of ferromagnetic behavior in the as-milled powders was observed at higher temperatures (>750 K) as compared to bulk Ni (~630 K). On the other hand, annealing of as-milled powders showed a large reduction in magnetic moment and the rate of decrease of moment strongly depends on the milling conditions. The observed properties are discussed on the basis of crystallite size variation, defect density, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion.

Item Type: Journal Item
Copyright Holders: 2015 Elsevier B.V.
ISSN: 0304-8853
Keywords: NiO powder; ferromagnetism; antiferromagnetism; microstructure; annealing effect; defect density
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Engineering and Innovation
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 42511
Depositing User: Satheesh Krishnamurthy
Date Deposited: 17 Apr 2015 09:43
Last Modified: 24 Mar 2017 06:50
URI: http://oro.open.ac.uk/id/eprint/42511
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