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Title: Size-dependent shifts of the Néel temperature and optical band-gap in NiO nanoparticles

Bulk NiO is a well-known antiferromagnet with Neel temperature T{sub N}(∞) = 524 K and an optical band-gap E{sub g} = 4.3 eV. With decrease in particle size D from 40 nm to 4 nm of NiO, systematic changes of T{sub N} and E{sub g} are observed and discussed here. From magnetic measurements, the changes in T{sub N} with D are found to fit finite-size scaling equation T{sub N}(D) = T{sub N}(∞) [1 − (ξ{sub o}/D){sup λ}] with λ = 3.2 ± 0.5 and ξ{sub o} = 3.2 ± 0.2 nm, in good agreement with the predictions for a Heisenberg system. The observed blue shifts of E{sub g} with decrease in D reaching E{sub g} = 5.12 eV for D ∼ 4 nm are likely due to quantum confinement and non-stoichiometry.
Authors:
 [1] ; ;  [2]
  1. Department of Physics, Indian Institute of Technology, Guwahati, Assam 781039 (India)
  2. Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States)
Publication Date:
OSTI Identifier:
22258674
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 21; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CONFINEMENT; EQUATIONS; NANOSTRUCTURES; NEEL TEMPERATURE; NICKEL OXIDES; PARTICLE SIZE; PARTICLES; SCALING