Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

Abstract

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

The Effect of Zn-Substitution on the Morphological, Magnetic, Cytotoxic, and In Vitro Hyperthermia Properties of Polyhedral Ferrite Magnetic Nanoparticles

“…The vertical black dashed lines in Figure 2 clearly reveal that the diffraction peaks were progressively shifted towards lower angles when going from ZnF01 to the ZnF10 sample. This effect was also observed in other studies, and it was attributed to the positioning of Zn 2+ ions in tetrahedral sites of the spinel crystalline structure upon synthesis [34,36,40,42,46]. The insertion of Zn 2+ ions, which have a larger radius than trivalent Fe 3+ , in tetrahedral sites, expands the crystalline structure of ZnF particles, leading to an increase in the lattice parameter.…”

“…As indicated by the dashed line in Figure 3, the dominant vibration mode shifts towards lower wavenumbers with increasing Zn concentration, from 574 cm −1 for the ZnF01 sample to 560 cm −1 for ZnF10 particles. This trend was interpreted in the literature in the light of a gradual substitution of Fe 3+ ions by Zn 2+ ones in tetrahedral sites of the spinel structure [36,39]. The light green and blue rectangles in Figure 3 delimit the regions of the FT-IR spectrum dominated by absorption bands of PEG200 (750-1250 cm −1 , 2750-3100 cm −1 ) and acetate (1350-1750 cm −1 ), respectively.…”

“…A literature review reveals that the thermal decomposition technique enables the formation of Zn substituted MNPs, exhibiting a well-defined shape that is not affected when modifying the Zn dopant concentration within their structure [31,32]. Instead, the rest of the synthesis methods employed for the elaboration of Zn ferrites, as co-precipitation, microwave-assisted, hydrothermal, and polyol [34,[36][37][38][39][42][43][44][45], have shown important morphological modifications of the resulting ZnF particles. A decrease in their size and variations in their shapes were observed when the Zn dopant level within the spinel structure was increased.…”

“…In most cases, this method enables the formation of secondary phases as wüstite [35]. Therefore, the most popular approach utilized co-precipitation of metal chloride or nitrate salts as it is quick, simple, and with low costs [27,[36][37][38][39][40][41]. The resulting ZnF-particles are, in the majority of cases, polydisperse in size and shape.…”

Specific Absorption Rate Dependency on the Co2+ Distribution and Magnetic Properties in CoxMn1-xFe2O4 Nanoparticles

“…The mixed ferrite nanoparticles have shown improved efficacy for magnetic hyperthermia, which can be attributed to the crystallite anisotropy manipulated by the exchange coupling of Mn 2+ , Co 2+ , and Fe 3+ cations in the spinel lattice with oxygen atoms [ 15 ]. Kerroum et al have reported SAR dependency on field strength in the superparamagnetic nanoparticle system of Zn x Fe 3-x O 4 ( x = 0.0–0.5) with particle size of 16 nm, synthesized using the chemical co-precipitation method [ 16 ]. The saturation magnetization (M s ) of nanoparticles was increased up to 120 Am 2 /kg for x = 0.3 by homogeneous zinc replacement of iron cations into the magnetite crystallite structure.…”