Lanthanum ion substituted cobalt ferrite nanoparticles and their hyperthermia efficiency

Highlights: • We examined the impact of substituting of rare earth La³⁺ ions into the B2-sites of Co-ferrite nanoparticles. • La-doping into the Co-ferrite nanoparticles allowed tuning the magnetocrystalline anisotropy and saturation magnetization. • Improved hyperthermia response was observed with the La-doped Co-ferrite nanoparticles, and an enhancement of specific loss power with increased viscosity occurred. We investigated the structural, compositional, and magnetic properties as well as the AC magnetic hyperthermic response of ${\text{CoFe}}_{2-x}{\text{La}}_x{\text{O}}_4$ $(x=0.0\text{,}0.2\text{,}0.5)$ nanoparticles. We found that the La³⁺ ions substituted into the Fe³⁺ ion sites, and resulted in an increased magnetocrystalline anisotropy with x, and altered the time-dependent magnetism. To provide a better understanding of the AC magnetic hyperthermia response, a series of temperature versus time measurements were done by varying the magnetic field amplitude, the carrier medium viscosity and the concentration of the nanoparticles as parameters that governed the heating efficiency. A decrease of specific loss power was observed with an increase of the viscosity of the carrier medium for $x=0$ and $x=0.25$ substituted Co-ferrite nanoparticles, while a small increase was observed with the $x=0.1$ La³⁺ substituted Co-ferrite nanoparticles (due to their higher intrinsic magnetocrystalline anisotropy).