Optimization of Magnetic Cobalt Ferrite Nanoparticles for Magnetic Heating Applications in Biomedical Technology

Abstract

Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (HC). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate (SAR). In the first series, CoxFe3−xO4 particles were synthesized with x = 1 and a structured variation of synthesis conditions, including those of the used atmosphere (O2 or N2). In the second series, particles with x = 0 to 1 were synthesized to study the influence of the cobalt fraction on the resulting magnetic and structural properties. Crystallite sizes of the resulting particles ranged between 10 and 18 nm, while maximum coercivities at room temperatures of 60 kA/m for synthesis with O2 and 37 kA/m for N2 were reached. Magnetization values at room temperature and 2 T (MRT,2T) up to 60 Am2/kg under N2 for x = 1 can be achieved. Synthesis parameters that lead to the formation of an additional phase when they exceed specific thresholds have been identified. Based on XRD findings, the direct correlation between high-field magnetization, the fraction of this antiferromagnetic byphase and the estimated transition temperature of this byphase, extracted from the Mössbauer spectroscopy series, we were able to attribute this contribution to akageneite. When varying the cobalt fraction x, a non-monotonous correlation of HC and x was found, with a linear increase of HC up to x = 0.8 and a decrease for x > 0.8, while magnetometry and in-field Mössbauer experiments demonstrated a moderate degree of spin canting for all x, yielding high magnetization. SAR values up to 480 W/g (@290 kHz, 69 mT) were measured for immobilized particles with x = 0.3, whit the external field amplitude being the limiting factor due to the high coercivities of our particles.

Impact of CoFe2O4 Magnetic Nanoparticles on the Physical and Mechanical Properties and Shape Memory Effect of Polylactide

“…Cobalt ferrite (CoFe 2 O 4 ) MNPs are of particular interest for magnetic hyperthermia due to their large cubic magneto-crystalline anisotropy and high coercivity value [55]. Ferrite nanomaterials with a spinel structure, including cobalt-spinel ferrite, possess high saturation magnetization, high permeability, and no preferred direction of magnetization as compared to widely studied iron oxides [56].…”

Magnetic Barium Hexaferrite Nanoparticles with Tunable Coercivity as Potential Magnetic Heating Agents

“…By using thermal markers, the assays could potentially be used with optically dense and colored sample materials, like blood. To increase the particles’ coercivity, apart from introducing shape anisotropy to iron oxide nanoparticles by synthesizing cubes, rods or discs [ 7 , 8 , 9 ], or increasing the size of single-domain iron oxide particles [ 10 , 11 , 12 ], ferrites like cobalt or barium ferrite can be used [ 13 , 14 , 15 , 16 ]. These materials exhibit larger anisotropies, which is why the barium hexaferrite BaFe 12 O 19 is a well-known material for magnetic storage [ 17 ] or for permanent magnets [ 18 ].…”