Model Driven Optimization of Magnetic Anisotropy of Exchange-Coupled Core–Shell Ferrite Nanoparticles for Maximal Hysteretic Loss

Abstract

This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g. size, magnetization, and magnetic anisotropy), and extrinsic properties of the applied fields (e.g. frequency, field strength). Often, the biomedical hyperthermia application limits flexibility in setting of many parameters (e.g. nanoparticle size and mobility, field strength and frequency). We show that core-shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the crystal anisotropy contribution of the Co ferrite phase to the nanoparticles total anisotropy is developed. The experimental results confirm that this framework predicts the hysteretic heating loss correctly when including non-linear effects in an effective susceptibility. Hence, we provide a guide on how to characterize the magnetic anisotropy of core-shell magnetic nanoparticles, model the expected heat loss and therefore, synthesize tuned nanoparticles for a particular biomedical application.

Dissociation coefficients of protein adsorption to nanoparticles as quantitative metrics for description of the protein corona: A comparison of experimental techniques and methodological relevance

“…[37], imaged with negative staining. Note that here BSA was linked chemically to the NP surface with EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) chemistry.…”

Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles

“…Core/shell architecture has acquired increasing interest due to the possibility of combining different materials and fabricating nanostructures with improved characteristics [1, 2]. In addition to varying size, shape, and composition, tuning of magnetic properties through the interface coupling of different magnetic materials becomes a prevailing strategy, introducing a new variable for the rational material design and property control in fundamental science and technological applications [3, 4].…”

Exploring Reaction Conditions to Improve the Magnetic Response of Cobalt-Doped Ferrite Nanoparticles

“…According to Stoner–Wohlfarth theory [33], blocking temperatures are proportional to the energy barrier E B between equivalent easy directions:$T_B=\frac{E_B}{\ln false({\tau }_m/{\tau }_{0}false)k_B}$ where k B is the Boltzmann constant and τ m represents the inverse of the frequency of jump attempts, assuming an Arrhenius-type time relaxation where τ 0 is the time window of the experiment. The effective magnetic anisotropy, K eff , is defined by E B = K eff V , being V the volume of the particle and it is determined by the shape, surface and magneto-crystalline anisotropy ( K c ) of the material [34]. Nevertheless, another contribution to the effective magnetic anisotropy due to dipolar interactions among the nanoparticles can appear.…”

“…These < T B > values can be used to estimate the effective anisotropy constants by means of Equation (1), however, from this equation the calculated K eff would be indicative of the anisotropy at temperatures close to the maximum of the ZFC , which varies from one sample to another. These data are not comparable, as Co containing nanoparticles show a significant variation of anisotropy constant with temperature [34]. Therefore, the determination of effective anisotropy constants at 0 K for all samples would become more useful in order to establish comparisons among them.…”

“…The values obtained vary in the range between 428 and 835 kJ/m 3 , which have been used to calculate the theoretical content of cobalt in these ferrites (0.02 < x < 0.08), with the formula proposed by Zhang et al [34] (Table 2). Although smaller values than those obtained from ICP appear, it is notable that these values would reflect estimated Co contents in a magnetite unit cell and ICP values of the overall concentrations, in spite of being inside the cell or as a segregated phase.…”