Influence of Grain Size Dispersion on the Magnetic Properties of Nanogranular BaTiO<SUB>3</SUB>-CoFe<SUB>2</SUB>O<SUB>4</SUB> Thin Films

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). Their structural and magnetic properties were characterized. The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation were observed. The lattice parameter of the CoFe2O4 was always smaller than the bulk value indicating that the cobalt ferrite was under compressive stress. From atomic force microscopy a broad distribution of grain sizes was observed in the nanocomposites, with a significant amount of smaller grains (<40 nm) from the CoFe2O4 phase. The magnetic measurements show an increase of the magnetic moment from the low concentration region where the magnetic grains are more isolated and their magnetic interaction is small, towards the bulk value for higher CoFe2O4 content in the films. A corresponding decrease of coercive field with increasing cobalt ferrite concentration was also observed, due to the higher inter-particle magnetic interaction (and reduced stress) of the agglomerated grains.

Octadecylamine-Mediated Versatile Coating of CoFe2O4 NPs for the Sustained Release of Anti-Inflammatory Drug Naproxen and in Vivo Target Selectivity

“…The minor variation of lattice parameter toward larger values than the bulk's (8.3919 Å), suggests that the unit cell is under stress. 27 EDS analysis showed that the composition of the samples varied from the generic formula of CoFe 2 O 4 , as shown in Table 1.…”

Unveiling the Physicochemical Features of CoFe2O4 Nanoparticles Synthesized via a Variant Hydrothermal Method: NMR Relaxometric Properties

“…The minor variation of lattice parameter from the value of bulk cobalt ferrite (8.3919 Å) indicated that the unit cell is under stress. 22 EDS analysis showed that CF3 and CF4 samples had similar composition with the generic formula of CoFe 2 O 4 , while sample CF1 was found to be iron rich by both EDS and ICP-OES analysis (Table 1). TEM analysis was used for the determination of the mean size, size distribution, and morphology of the nanoparticles (Figure 2, Figure 1S).…”

“…The lattice constants of samples CF1–4 were also calculated and found to be 8.393(0), 8.394(0), 8.389(0), and 8.391(1) Å, respectively. The minor variation of lattice parameter from the value of bulk cobalt ferrite (8.3919 Å) indicated that the unit cell is under stress …”