Effects of Ce³⁺ doping on the structural, magnetic and hyperfine properties of cobalt ferrite nanoparticles

Abstract

We report on the structural, magnetic, and hyperfine properties of cobalt ferrite nanoparticles substituted with a minor fraction of Ce³⁺. Sol–gel technique was utilized to prepare ${\text{CoCe}}_{{\text{x}}} {\text{Fe}}_{{{2} - {\text{x}}}} {\text{O}}_{{4}} {\text{ (x}} = {0}{\text{.0}},{0}{\text{.05}}\;{\text{and}}\;0.10)$ nanoparticles. Rietveld refinement of x-ray diffraction patterns show that all the samples crystallize in a face-centered cubic symmetry. The cell parameter increases while the grain size decreases with increasing ${\text{Ce}}^{{{3} + }}$ concentration. Magnetic measurements show a reduction of saturation magnetization, remanent magnetization and total magnetic moment with increasing ${\text{Ce}}^{{{3} + }}$ content. Furthermore, ${\text{M}}\left( {\text{T}} \right)$ curves indicate that ${\text{CoCe}}_{{\text{x}}} {\text{Fe}}_{{{2} - {\text{x}}}} {\text{O}}_{{4}}$ powders show various magnetic phases before paramagnetic state: region (i) canted antiferromagnetic or weak-ferromagnetic state with its respective Morin temperature (T_M), (ii) canted antiferromagnetic with the corresponding Néel temperature (T_N). Mössbauer measurements were performed as well and the hyperfine field ${\text{H}}_{{{\text{hf}}}}$ was related to Ce content. The magnitudes of isomer shift (IS) of all samples show that iron are present in trivalent state $\left( {{\text{Fe}}^{{{3} + }} } \right)$.