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Structural and Magnetic Properties of Nanogranular BaTiO3-CoFe2O4 Thin Films Deposited by Laser Ablation on Si/Pt Substrates

Published online by Cambridge University Press:  26 February 2011

José Barbosa ,
Bernardo Almeida ,
Jorge A. Mendes ,
Anabela G. Rolo ,
João P. Araújo  and
João B. Sousa
José Barbosa
Affiliation:
jbarbosa@fisica.uminho.pt, Universidade do Minho, Departamento de Física, Campus de Gualtar, Braga, 4710-057 Braga, Portugal
Bernardo Almeida
Affiliation:
bernardo@fisica.uminho.pt, Universidade do Minho, Departamento de Física, Campus de Gualtar, Braga, 4710-057 Braga, Portugal
Jorge A. Mendes
Affiliation:
jamendes@fisica.uminho.pt, Universidade do Minho, Departamento de Física, Campus de Gualtar, Braga, 4710-057 Braga, Portugal
Anabela G. Rolo
Affiliation:
arolo@fisica.uminho.pt, Universidade do Minho, Departamento de Física, Campus de Gualtar, Braga, 4710-057 Braga, Portugal
João P. Araújo
Affiliation:
jearaujo@fc.up.pt, Universidade do Porto, Dep. de Física and IFIMUP, Rua Campo Alegre, 687, Porto, 4169-007 Porto, Portugal
João B. Sousa
Affiliation:
jbsousa@fc.up.pt, Universidade do Porto, Dep. de Física and IFIMUP, Rua Campo Alegre, 687, Porto, 4169-007 Porto, Portugal
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Abstract

Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt ferrite concentrations (x). The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinnel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation was observed. As the concentration of the cobalt ferrite increased, the grain size of the BaTiO3 phase decreased, from 91nm to 30nm, up to 50% CoFe2O4 concentration, beyond which the BaTiO3 grain size take values in the range 30-35nm. On the other hand the cobalt ferrite grain size did not show a clear trend with increasing cobalt ferrite concentration, fluctuating in the range 25nm to 30nm. The lattice parameter of the CoFe2O4 phase increased with increasing x. However, it was always smaller than the bulk value indicating that, in the films, the cobalt ferrite was under compressive stress that was progressively relaxed with increasing CoFe2O4 concentration. The magnetic measurements showed a decrease of coercive field with increasing x, which was attributed to the relaxation of the stress in the films and to the increase of particle agglomeration in bigger polycrystalline clusters with increasing cobalt ferrite concentration.

Keywords

compositestructuralmagnetic properties
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 966: Symposium T – Ferroelectrics and Multiferroics , 2006 , 0966-T03-24
Copyright
Copyright © Materials Research Society 2007

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References

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