Strong modulation effects on magnetoelectric behavior of Co-ferrite nanoparticles incorporated in ZnO medium in nano-regime synthesized in chemical routes
Résumé
The dielectric and piezoelectric host of ZnO nanoparticles was chosen for the incorporation of ferrimagnetic and magneto-
strictive CoFe 2O4 (CFO) nanoparticles to achieve magnetic and electric orderings simultaneously, under coupled conditions.
Two composite samples of CFO@ZnO including the bare one, for comparison, were synthesized under different chemical
reaction conditions to observe the influence of particle size on the different magneto-electric properties. The modified syn-
thesis routes were considered due to which modified magnetoelectric behaviors were found in the samples. The particle size
plays an important role in the different physical properties. Rietveld analyses of the recorded XRD patterns of all samples
confirmed pure phase formation and also provide various structural information to understand the magnetoelectric behavior
of these samples. Particle size obtained from this for CFO@ZnO-1 is ~ 20 nm and for CFO@ZnO-2 is ~ 10.9 nm. This size
difference is also reflected in the observed FESEM and TEM micrographs. The EDAX spectra and mapping confirm the
absence of impurity elements and the uniform distribution of constituent phases of composites. The dielectric properties of
ZnO are substantially modified by the presence of CFO nanoparticles in each composite sample and this also depends on
the size of the nanoparticles. Dielectric spectroscopy studied in the temperature range 300–425 K, provides detailed electri-
cal properties of both composites. Both composites show enhanced dielectric constant with a very low dielectric loss along
with strong magnetic properties. Magnetic investigations were performed on all samples with a maximum applied field of
3 T at different temperatures ranges with a minimum value of 10 K to a maximum value of 850 K. Ferrimagnetic behavior
and Curie temperature were observed in case of CFO and CFO@ZnO-1 and presence of superparamagnetism was detected
in CFO@ZnO-2. Presence of ferroelectricity was observed in composites at 300 K and 273 K. Coupling between magnetic
and electric orderings generated due to magnetostriction of CFO and piezoelectricity of ZnO together with crystallographic
strain originated from structural mismatch of these components. This magnetoelectric coupling was investigated through
magnetocapacitance measurements, which show a high value of magnetocapacitance (~ 10%) indicating the presence of
good magnetoelectric coupling. Thus, the present composite having good magnetoelectric coupling may be interesting in
the family of multiferroics.