Magnetic properties of nanoscaled paramelaconite Cu sub(4)O sub(3-x) (x=0.0 and 0.5)

Pure paramelaconite Cu sub(4)O sub(3-x) has been prepared in the form of nanoparticles with 56 nm in diameter. This mixed valency oxide crystallizes in a tetragonal lattice with 4 unit formulae and forms a pyrochlore structure which manifests in two stoichiometric forms; Cu sub(4)O sub(3) and Cu sub...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2015-01, Vol.373, p.183-187
Main Authors: Djurek, D, Prester, M, Drobac, Dj, Ivanda, M, Vojta, D
Format: Article
Language:English
Subjects:
Antiferromagnetism
Copper
Crystal defects
DEFECTS
Ferromagnetism
Inversions
LATTICE DEFECTS
MAGNETIC PROPERTIES
MICROSTRUCTURES
Nanostructure
Order disorder
ORDER DISORDER RELATIONSHIPS
Symmetry
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Summary:Pure paramelaconite Cu sub(4)O sub(3-x) has been prepared in the form of nanoparticles with 56 nm in diameter. This mixed valency oxide crystallizes in a tetragonal lattice with 4 unit formulae and forms a pyrochlore structure which manifests in two stoichiometric forms; Cu sub(4)O sub(3) and Cu sub(4)O sub(2.5), the latter form having two oxygen vacancies per unit cell. Magnetic lattice consists of Cu spin 1/2, and both stoichiometric forms obey transition to the antiferromagnetic state at T sub(N)=45-55 K. Defect free Cu sub(4)O sub(3) is indicated by an inversion symmetry and exhibits both antiferromagnetic and ferromagnetic state, where the latter is supposedly due to the superexchange interaction in Cu-O(1n)-Cu bonds. An additional magnetic transition was observed in Cu sub(4)O sub(3) at T=120 K, probably as a result of an incommensurate ordering. Absence of an inversion symmetry in the oxygen defect Cu sub(4)O sub(2.5) results in a long range Dzyaloshinsky-Moriya interaction accompanied by the strong superparamagnetism.
ISSN:0304-8853
DOI:10.1016/j.jmmm.2014.04.015