Magnetite and gallium substituted cuboferrites with a composition of Ga_xFe_3−xO₄ (0 ≤ x ≤ 1.4) were fabricated by thermal decomposition from acetylacetonate salts. The effect of Ga³⁺ cation substitution on the structural and thermomagnetic behavior of 4–12 nm sized core-shell particles was explored by X-ray and neutron diffraction, small angle neutron scattering, transmission electron microscopy, Mössbauer spectroscopy, and calorimetric measurements. Superparamagnetic (SPM) behavior and thermal capacity against increasing gallium concentration in nanoferrites were revealed. The highest heat capacity typical for Fe₃O₄@Ga_0.6Fe_2.4O₄ and Ga_0.6Fe_2.4O₄@Fe₃O₄ is accompanied by a slight stimulation of fibroblast culture growth and inhibition of HeLa cell growth. The observed effect is concentration dependent in the range of 0.01–0.1 mg/mL and particles of Ga_0.6Fe_2.4O₄@Fe₃O₄ design have a greater effect on cells. Observed magnetic heat properties, as well as interactions with tumor and healthy cells, provide a basis for further biomedical research to use the proposed nanoparticle systems in cancer thermotherapy (magnetic hyperthermia).

New data on gallium ferrite particles are reported. The results of studies of Fe₃O₄/Ga_xFe_3 – xO₄ and Ga_xFe_3 – xO₄/Fe₃O₄ (x = 0.2, 0.4, 0.6 and 0.8) nanoparticles by X-ray and neutron diffraction, small angle neutron scattering, transmission electron microscopy, magnetization measurements, and Mössbauer spectroscopy. The cubic core–shell ferrites structures were confirmed as single phases with a cell parameter of ∼8.388 Å independent of gallium content. The lack of preferences in occupancies of gallium sites was confirmed. The magnetic structure at room temperature, the stability of a disaggregated dispersion of nanoparticles in the temperature range 20–50°C, the radii of the cores, and the thickness of the coating layers, as well as the specific absorption of electromagnetic radiation rates were characterized.

The structural, magnetic and calorimetric properties of Fe_2.4Ga_0.6O₄ nanoferrite have been investigated. X-ray and neutron diffraction coupled analyses using Rietveld refinements have shown that the samples under investigation, obtained by different bottom-up methods, crystalize with a cubic structure in the $Fd\overline{3}m$ space group (N° 227). The Ga³⁺ ions preferentially occupying the tetrahedral sublattice of the inverse spinel partly screen the dipole–dipole interactions and lead to the reduction of the magnetic response of Fe³⁺ ones. Calorimetric measurements confirm that the nanosized Fe_2.4Ga_0.6O₄ system weakly agglomerates and simultaneously collect and release optimal amount of heat under the influence of an alternating magnetic field with the 15.3 kA/m of maximum magnetic field strength and 532 kHz of frequency. The values of the specific absorption coefficients obtained for gallium ferrites, similar to those typical for cobalt ferrites used commercially in biomedicine, together with very low superparamagnetic blocking temperature validated by Mössbauer spectroscopy analysis, make the system an attractive therapeutic material.

Nanoparticles based on gallium ferrite are explored as potential agents for magnetic fluid hyperthermia due to their magnetic performance and biocompatibility. In this study, Ga_xFe_3−xO₄ systems (0 ≤ x ≤ 1) were synthesized by co-precipitation of iron chlorides, with part of the series modified by a chitosan shell. Structural analysis confirmed single-phase formation across the studied range, while microscopy revealed irregular morphology, broad size distribution, and aggregation into mass-fractal-like assemblies. Chitosan was observed to coat groups of particles rather than single crystallites. Under an alternating magnetic field, all samples exhibited efficient heating, with specific absorption rate values generally increasing with gallium content. The composition Ga_0.73Fe_2.27O₄ showed the highest SAR—83.4 ± 2.2 W/g at 2.8 mg/mL, 532 kHz, 15.3 kA/m, and SAR values rose with decreasing concentration. Cytotoxicity assays without magnetic activation indicated no harmful effect, while chitosan-coated nanoparticles enhanced fibroblast viability and lowered metabolic activity of HeLa cells. Higher Ga content (x = 0.66) combined with chitosan modification was identified as optimal for hyperthermia. The results demonstrate the biomedical potential of these nanoparticles, while emphasizing the need to reduce shape heterogeneity, aggregation, and sedimentation for improved performance.

The influence of the surface modification on the magnetism of 4–14 nm sized core and core/shell gallium ferrites obtained by different preparation methods (Massart’s and thermal decomposition from acetylacetonates) was studied. The physical properties of Ga_xFe_3-xO₄ were investigated in a wide range of Ga admixtures 0 ≤ x ≤ 1.5. Ga ions location at 8a or/and 16d positions of a spinel structure depends on the synthesis method and has a pronounced effect on the superparamagnetic properties of nanoparticles. Magnetization and Mössbauer experiments show the dominant superparamagnetic contribution for the nanoparticles with x > 0.8 with the blocking temperature TB significantly below 200 K. Surface-modified nanoferrites disclosed spontaneous magnetization that does not exceed 60 emu/g.