Magnetic Coercivity Research Articles

Element-Specific Study of Magnetic Anisotropy and Hardening in SmCo5-xCux Thin Films.

This work investigates the effect of copper substitution on the magnetic properties of SmCo5 thin films synthesized by molecular beam epitaxy. A series of thin films with varying concentrations of Cu were grown under otherwise identical conditions to disentangle structural and compositional effects on the magnetic behavior. The combined experimental and theoretical studies show that Cu substitution at the Co3g sites not only stabilizes the formation of the SmCo5 structure but also enhances magnetic anisotropy and coercivity. Density functional theory calculations indicate that Sm(Co4Cu3g)5 possesses a higher single-ion anisotropy as compared to pure SmCo5. In addition, X-ray magnetic circular dichroism reveals that Cu substitution causes an increasing decoupling of the Sm 4f and Co 3d moments. Scanning transmission electron microscopy confirms predominantly SmCo5 phase formation and reveals nanoscale inhomogeneities in the Cu and Co distribution. Our study based on thin film model systems and advanced characterization as well as modeling reveals novel aspects of the complex interplay of intrinsic and extrinsic contributions to magnetic hysteresis in rare-earth-based magnets, i.e., the combination of increased intrinsic anisotropy due to Cu substitution and the extrinsic effect of inhomogeneous elemental distribution of Cu and Co.

Magnetic Ni‐Nanoinclusions in VO2 Thin Films for Broad Tuning of Phase Transition Properties

AbstractMott insulator VO2 exhibits an ultrafast and reversible semiconductor‐to‐metal transition (SMT) near 340 K (67 °C). In order to fulfill the multifunctional device applications, effective transition temperature (Tc) tuning as well as integrated functionality in VO2 is desired. In this study, multifunctionalities including tailorable SMT characteristics, ferromagnetic (FM) integration, and magneto‐optical (MO) coupling, have been demonstrated via metal/VO2 nanocomposite designs with controlled morphology, i.e., a two‐phase Ni/VO2 pillar‐in‐matrix geometry and a three‐phase Au/Ni/VO2 particle‐in‐matrix geometry. Evident Tc reduction of 20.4 to 54.9 K has been achieved by morphology engineering. Interestingly, the Au/Ni/VO2 film achieves a record‐low Tc of 295.2 K (22.2 °C), slightly below room temperature (25 °C). The change in film morphology is also correlated with unique property tuning. Highly anisotropic magnetic and optical properties have been demonstrated in Ni/VO2 film, whereas Au/Ni/VO2 film exhibits isotropic properties because of the uniform distribution of Au/Ni nanoparticles. Furthermore, a strong MO coupling with enhanced magnetic coercivity and anisotropy is demonstrated for both films, indicating great potential for optically active property tuning. This demonstration opens exciting opportunities for the VO2‐based device implementation towards smart windows, next‐generation optical‐coupled switches, and spintronic devices.

Origin of Enhancement of Orbital Magnetic Moment in SiO2-Coated Fe3O4 Nanocomposites Studied by X-ray Magnetic Circular Dichroism.

In this study, magnetic Fe3O4 nanoparticles (NPs) were dispersed uniformly by varying the thickness of the SiO2 coating, and their electronic and magnetic properties were investigated. X-ray diffraction confirmed the structural configuration of monophase inverse-spinel Fe3O4 NPs in nanometer size. Scanning electron microscopy revealed the formation of proper nonporous crystallite particles with a clear core-shell structure with silica on the surface of Fe3O4 NPs. The absorption mechanism studied through the zeta potential indicates that SiO2-coated Fe3O4 nanocomposites (SiO2@Fe3O4 NCs) possess electrostatic interactions to control their agglomeration in stabilizing suspensions by providing a protective shield of amorphous SiO2 on the oxide surface. High-resolution transmission electron microscopy images demonstrate a spherical morphology having an average grain diameter of ∼11-17 nm with increasing thickness of SiO2 coating with the addition of a quantitative presence and proportion of elements determined through elemental mapping and electron energy loss spectroscopy studies. Synchrotron-based element-specific soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) techniques have been involved in the bulk-sensitive total fluorescence yield mode to understand the origin of magnetization in SiO2@Fe3O4 NCs. The magnetization hysteresis of Fe3O4 was determined by XMCD. At room temperature, the magnetic coercivity (Hc) is as high as 1 T, which is about 2 times more than the value of the thin film and about 5 times more pronounced than that of NPs. For noninteracting single-domain NPs with the Hc spread from 1 to 3 T, the Stoner-Wohlfarth model provided an intriguing explanation for the hysteresis curve. These curves determine the different components of Fe oxides present in the samples that derive the remnant magnetization involved in each oxidation state of Fe and clarify which Fe component is responsible for the resultant magnetism and magnetocrystalline anisotropy based on noninteracting single-domain particles.

Au@Fe3O4 NANOPARTICLES: PREPARATION, CHARACTERIZATION AND CYTOTOXIC EVALUATION

Gold-coated iron oxide nanoparticles are a class of potential theranostic nanoparticles that have been studied for their multitude of magnetic and optical properties with possible medical applications. In this work, spherical Au@Fe3O4 nanoparticles were successfully synthesized from Fe electrodes immersed in HAuCl4 solution using a very simple method - pulsed plasma in liquid, without any dopants or special conditions for stabilization. Vibrating sample magnetometer indicated ferromagnetic behavior of the particles at room temperature with coercivity and saturation magnetization of Hc=175 and Ms= 3.56 emu/g, respectively. Face-centered cubic Au and spinel inverse structure of FCC- Fe3O4 were determined by X-Ray diffraction analysis. High-resolution transmission electron microscopic analysis revealed that Fe3O4 particles with 14 nm in size are connected to 18 nm Au particles. The cytotoxicity of the nanoparticles was evaluated using a XTT assay on Hela cells, revealing very low (cell viability: 98-89% with Fe3O4 and 99-91% for Au@Fe3O4 NPs). This indicates that Au improves biocompatibility of magnetic nanoparticles, enabling their application in biomedicine

Facile and fast synthesis of highly ordered L10-FeNi nanoparticles

The chemically ordered L10-FeNi alloy is a promising candidate for next generation rare-earth-free permanent magnets, which can revolutionize the high-performance magnets market currently dominated by Nd-Fe-B. Despite many efforts, the experimental results fall short of theoretical predictions, and current approaches are not suitable for industrial implementation. In this work, we propose an innovative and efficient synthesis method that exploits the natural order of a crystalline Ni/Fe complex, which closely mimics the atomic organization in the L10 structure, to drive the formation of the ordered phase. By low-temperature reduction of the complex salt, carbon coated aggregates of FeNi alloy nanoparticles (20 – 120 nm) with a >55% of L10 phase, high coercivity (up to 65 mT) and large saturation magnetization (∼ 140 Am2/kg) were obtained. The results pave the way for the development of a novel and sustainable route to produce high-anisotropy FeNi nanoparticles of potential interest for next generation critical-element-free permanent magnets.

Quantized resistance revealed at the criticality of the quantum anomalous Hall phase transitions

In multilayered magnetic topological insulator structures, magnetization reversal processes can drive topological phase transitions between quantum anomalous Hall, axion insulator, and normal insulator states. Here we report an examination of the critical behavior of two such transitions: the quantum anomalous Hall to normal insulator (QAH-NI), and quantum anomalous Hall to axion insulator (QAH-AXI) transitions. By introducing a new analysis protocol wherein temperature dependent variations in the magnetic coercivity are accounted for, the critical behavior of the QAH-NI and QAH-AXI transitions are evaluated over a wide range of temperature and magnetic field. Despite the uniqueness of these different transitions, quantized longitudinal resistance and Hall conductance are observed at criticality in both cases. Furthermore, critical exponents were extracted for QAH-AXI transitions occurring at magnetization reversals of two different magnetic layers. The observation of consistent critical exponents and resistances in each case, independent of the magnetic layer details, demonstrates critical behaviors in quantum anomalous Hall transitions to be of electronic rather than magnetic origin. Our finding offers a new avenue for studies of phase transition and criticality in QAH insulators.

Effect of diffusing TbH3 on magnetic, corrosion and mechanical properties of NdFeB magnet

Grain boundary diffusion can enhance the coercivity of NdFeB magnets with low consumption of heavy rare earths Dy/Tb. This work systematically studied the effects of diffusing TbH3 on the magnetic, corrosion and mechanical properties of NdFeB magnet. The results show that the remanence Br and maximum energy product (BH)max of magnets slightly decreased after diffusion, while coercivity increased from 14.47 kOe to 22.08 kOe with 0.20 wt% Tb usage. The formation of Tb-rich shell and RE-(FeO) metallic-type grain boundary phases attribute to the enhancement of coercivity. The fracture and corrosion behavior of NdFeB magnet are discussed before and after diffusion. This study provides an experiment and theoretical basis for the industry fabrication of high-performance magnet with low heavy rare earth.

Effect of non-rare-earth element enrichment on in-the-column secondary electron image contrast of Nd-rich phases in Nd-Fe-B sintered magnets

In-the-column secondary electron (SE) imaging has demonstrated an important role in identifying various Nd-rich phases in Nd-Fe-B sintered magnets at a microscale field of view. It is well known that modifying the microstructure of Nd-Fe-B sintered magnets by adding non-rear-earth (NRE) elements dissolved into the intergranular Nd-rich phases during post-sinter annealing can effectively increase the magnet coercivity. However, the effect of NRE element enrichment on in-the-column SE image contrast of Nd-rich phases has not received much attention. In this study, we have combined a focused ion/electron dual beam system (FIB/SEM) and a scanning/transmission electron microscope (S/TEM) to investigate the in-the-column SE image contrast, structure, and element distribution of intergranular Nd-rich phases in commercial heavy-rare-earth (HRE) free Nd-Fe-B sintered magnets. In-lens SE imaging revealed that Cu, Co, or Al-enriched neodymium oxides with fcc, Ia3¯-type, or amorphous structures are brighter than the Nd2Fe14B matrix at an accelerating voltage of 2 kV and a working distance of 4 mm. Bright stripes inside the intergranular fcc NdOx were also visible in high-resolution through-the-column SE imaging, reflecting the nanoscale composition variation with Co or Cu enrichment. Contrarily, at the same imaging conditions, the nearly pure fcc NdOx and Ia3¯-Nd2O3 exhibit darker than the Nd2Fe14B matrix in the in-lens SE image. It has been demonstrated that the in-lens SE image contrast of Nd-rich phases with respect to the Nd2Fe14B matrix remains constant by systematically adjusting the accelerating voltage from 2 kV to 5 kV and the working distance from 4 mm to 6 mm. Our research results suggest that low-voltage in-the-column SE imaging could be used to track element diffusion in triple junction and grain boundary Nd-rich phases of Nd-Fe-B sintered magnets during post-sinter annealing by in-situ MEMS heating in SEM.

Identification Morphology and Magnetic Properties Sedimentary Elements Between Fossils and Outcrops Around the Lusi River: A Case Study of Central Java, Indonesia

Lusi River flows in the middle of Grobogan Regency with a length of 234 km and an area of 3,656.78 km2. The warp river has many very diverse ends. One of them is the discovery of deer fossils estimated to be around 30,000 years ago and stored in the Pleistocene layer. There may be still many fossils stored in this layer that have never been studied. It is estimated that 80 % of fossils are incomplete because there are teeth attached to the fossils and the condition of the jaws is still neatly arranged. We get the magnetic susceptibility value around 1.3×10−8 - 37.8×10−8 m3/kg. Vibrating Sample Magnetometer confirm that value of magnetic saturation about 0.071 - 0.176 emu/gr, magnetic remanent about 0.0001 - 0.004 emu/gr, and magnetic coercivity around 10.969 - 115.278 Oe. X-Ray Diffractometer confirm the mineral is Calcite (CaCO3) and Quartz (SiO2). From the results we got, it can be confirmed that the fossils found at the bottom of the Lusi river have the same minerals and elements as environmental sediments. So, fossils can be said to have been sedimented over a long period of time in the Lusi River. HIGHLIGHTS We have some important things in this study: Lusi river is a place we found fossil Lusi river we found a poor magnetic mineral We get the magnetic properties of the transition from paramagnetic to diamagnetic GRAPHICAL ABSTRACT

Revealing the effect of rapid annealing on nano-crystallization behavior and soft magnetic properties of Fe–Co–B amorphous alloy

Rapid annealing (RA), or the application of a high temperature for a short duration, is an efficient strategy to promote the nano-crystallization of Fe-based amorphous alloys and improve their soft magnetic properties. Herein, the ternary Fe–Co–B amorphous alloy is investigated as a typical system to reveal the effect of RA on crystallization behavior and soft magnetic properties. It is found that the large superheating generated during RA significantly increases the homogenous nucleation rate of nanocrystals, while the short duration greatly inhibits the growth kinetics, yielding fine and dense nanograins in the amorphous matrix. The Fe–Co–B alloy shows optimized properties of low coercivity (5.6 A/m) and high saturation magnetization (1.87 T) after RA at 813 K for 3 s. In contrast, all superheating and long duration used in conventional annealing produce large and sparse grains with single crystal morphology and large coercivity above 30 A/m. This work reveals the thermodynamic and kinetic effects of RA on the nano-crystallization behavior of Fe-based amorphous alloys, showing that the RA treatment (high annealing temperature and short annealing time) can induce in-situ homogeneous nucleation and growth, which may help guide the design of Cu-free amorphous/nanocrystalline alloys with desirable soft magnetic properties.

Giant room-temperature modulation of magnetic anisotropy by electric fields in CoFeB/(011)-PMN-PT multiferroic heterostructures with two distinct initial magnetic anisotropies

This paper reports that the in situ growth magnetic field (Hg) during magnetic-phase CoFeB deposition impacts the electric-field control of magnetic anisotropy in Co40Fe40B20/(011)-Pb(Mg1/3Nb2/3)0.7Ti0.3O3 [CoFeB/(011)-PMN-PT] composite multiferroic heterostructures at room temperature. In the Hg1 mode (in situ Hg along the [011¯] direction of the ferroelectric PMN-PT substrate), the electric-field-controlled modulation ratios of the magnetic coercivity HC and saturation magnetic field HS are approximately −47% and +156%, respectively. However, in the Hg2 mode (in situ Hg along the [100] direction of the ferroelectric PMN-PT substrate) of the CoFeB/(011)-PMN-PT multiferroic heterostructure, the electric-field-controlled modulation ratios of the magnetic coercivity HC and saturation magnetic field HS can reach as high as +162% and +393%, respectively. Moreover, the electric-field-controlled magnetic coercive field HC exhibits a butterfly shape when plotted versus the applied electric fields in both modes, which matches the in-plane butterfly strain loop of the ferroelectric PMN-PT substrate. However, the electric-field-controlled saturation magnetic field HS presents a square loop, which is very consistent with the ferroelectric loop of the PMN-PT substrate. This result may be ascribed to the distinct pathway of the ferroelastic domain switching in the (011)-oriented PMN-PT substrate. This study provides a new idea for the design of spintronic devices based on multiferroic heterostructures.

Phase-Field Study of Exchange Coupling in Co-Pt Nonstandard Nanochessboards.

The Co-Pt binary system can form a two-phase nanochessboard structure comprising regularly aligned nanorods of magnetically hard tetragonal L10 phase and magnetically soft cubic L12 phase. This Co-Pt nanochessboard, being an exchange-coupled magnetic nanocomposite, exhibits a strong effect on magnetic domains and coercivity. While the ideal nanochessboard structure has tiles with equal edge lengths (a = b), the non-ideal or nonstandard nanochessboard structure has tiles with unequal edge lengths (a ≠ b). In this study, we employed phase-field modeling and computer simulation to systematically investigate the exchange coupling effect on magnetic properties in nonstandard nanochessboards. The simulations reveal that coercivity is dependent on the length scale, with magnetic hardening occurring below the critical exchange length, followed by magnetic softening above the critical exchange length, similar to the standard nanochessboards. Moreover, the presence of unequal edge lengths induces an anisotropic exchange coupling and shifts the coercivity peak with the length scale.

Effect of Cd2+ Substitution on Structural-Magnetic and Dielectric Properties of Ni-Cu-Zn Spinel Ferrite Nanomaterials by Sol-Gel.

CdxNi0.5-xCu0.2Zn0.3Fe2O4 (0 ≤ x ≤ 0.50) ferrite with a spinel structure was prepared using the sol-gel self-propagation method. The effects of Cd2+ doping on the structure, morphology, dielectric, and magnetic properties of Ni-Cu-Zn ferrite were examined using XRD, SEM, EDX, FTIR, MPMS, and dielectric tests. The cubic spinel structure was verified by XRD and FTIR analyses. The crystallite size and particle size information of the samples were obtained with XRD and SEM analysis. The sample particle size belonged to a class of nanoscale materials with a particle size range of 1-100 nm. The minor difference between the grain size and particle size indicated that the sample nanoparticles were composed of numerous microcrystals. The EDX spectra indicated that the samples contained all stoichiometric elements. MPMS was used to measure the hysteresis lines of the samples. According to the hysteresis line, the saturation magnetization intensity (Ms), coercivity (Hc), and magnetic moment (μB) of the sample increased and then decreased with the increase in cadmium concentration. The magnetization strength (Ms) is between 4-67 emu/g, and the coercivity (Hc) is between 9-46 Oe. The curves of the real part of the dielectric constant (ε'), the imaginary part of the dielectric constant (ε″), and the loss factor (tanδ) with frequency were measured in the frequency range 100 Hz-100 kHz by means of an impedance analyzer. The complex modulus spectrum was analyzed to understand the dynamics of the conduction process.

Low-temperature-sintering of Co2Z ferrite materials via Dy3+ ion doping for use in high-frequency applications

According to this study, Co2Z ferrite is suitable for applications in high-frequency antennas. Ba3Co2Fe24-xDyxO41 samples with different values of Dy3+ doping concentration (x) in the range of 0.00–0.25 were prepared in the study by employing solid-state sintering and 2.5 wt% Bi2O3 sintering aids. A systematic analysis of the physical phase structure, microstructure, and magnetic dielectric properties of the samples was also performed. The X-ray diffraction patterns of the samples showed that doping with Dy3+ ions and the addition of the Bi2O3 sintering aid had not changed the physical structure of the sample material, indicating that the material was still a Z-type hexagonal ferrite. In addition, according to the magnetic hysteresis loops of the samples, all six groups of them exhibited typical soft magnetic properties. With an increase in the Dy3+ ion doping concentration, the saturation magnetization intensity and coercivity of the samples initially increased and then decreased. The sample with a Dy3+ ion doping concentration of 0.15 had the most uniform grain distribution, largest density, and smallest porosity among the samples. Additionally, that sample had the maximum values of the real parts of the magnetic permeability (7.89) and permittivity (13.90) while having a low magnetic loss (tanδμ≤0.04) and a low dielectric loss (tanδε≤0.03). Thus, this type of magnetic dielectric materials will have significant potential for use in high-frequency antenna applications.

Optimizing microstructure, magnetic properties and mechanical properties of sintered NdFeB magnet by double alloy method and grain boundary diffusion

This paper presents improvements in the coercivity, mechanical strength, and corrosion resistance of NdFeB magnets by modifying their microstructure using the double alloy method and grain boundary diffusion. The coercivity of magnet increases significantly from 16.66 kOe to 23.78 kOe with 0.64 wt% Tb usage. The overall magnetic performance (OMP) (BH)max (MGOe) + Hcj (kOe) of diffusion magnet improves approximately 7.09%. Furthermore, the mechanical properties and corrosion resistance are enhanced through the diffusion process. The microstructure forms thin intergranular phases of RE-Fe-O and a double core-shell structure consisting of Dy and Tb. These modifications contributed to the improved properties of NdFeB magnets. The formation mechanism of double core-shell is analyzed in detail. This work proposes a viable method for preparing high comprehensive performance magnet with a low Dy/Tb content.

Magnetic coercivity control via buffer layer roughness in Pt/Co multilayers

Magnetic properties of thin metallic films are strongly dependent on the growth parameters. Therefore, fine-tuning these parameters is necessary to produce multilayers with specific physical properties required by various applications. Here, we present an efficient approach to tune the coercive field of magnetron sputtered Co/Pt multilayers using Au underlayer with variable thickness. We were able to control the interfacial roughness of the layers in the stack via the change of the Au underlayer thickness due to its island-like growth mechanism (Volmer-Weber mode). As the nominal thickness of Au increased, the islands grew in larger lateral size, resulting in higher surface roughness of the underlayer, which was transferred to subsequent interfaces. Magnetization measurements showed additional magnetic anisotropy promoted by this mechanism. Variating the thickness of the Au layer up to 20 nm, we changed the coercive field in the range from ∼ 200 Oe to ∼ 1100 Oe while maintaining a nearly constant saturation magnetization. Presented results demonstrate the possibility to precisely design magnetic properties of metallic multilayers for applications via buffer layer roughness engineering.

Synthesis, characterization, and applications of doped barium hexaferrites: A review

Barium hexaferrite is a ceramic material with a hexagonal crystal structure that is widely used in various applications such as microwave devices and, magnetic recording media due to its excellent magnetic and electromagnetic traits. This material is composed of barium, oxygen, and iron and has the chemical formula, BaFe12O19. The barium hexaferrite (BHF) exhibits magnetic anisotropy, high magnetization, and high coercivity, making it a preferred material for use in magnetic devices. This review paper presents an overview of the synthesis methods, crystal structure, magnetic traits, and various applications of BHF. The various synthesis approaches discussed include hydrothermal, microemulsion approach, solid-state approach, co-precipitation, and a few other techniques. The effect of various elemental doping on the optical, magnetic, electromagnetic, as well as the structural characteristics of BHF are discussed in detail. Additionally, the different applications of BHF are discussed, including its use in microwave devices, magnetic recording media, water purification, biomedical, and permanent magnet. This review provides a comprehensive assessment of the current state of knowledge on BHF, and highlights its potential for use in a number of technological applications.

Formation and magnetic enhancement mechanism of sandwich-structure grain boundary phase in Ce magnets

In this study, the formation mechanism of sandwich-structure grain boundary phase in sintered Ce magnets with various Pr-Nd-Al alloy additions is investigated in detail. The sandwich-structure grain boundary between the main phases is composed of RE6(Fe, TM)11Al3 phase at the center and symmetrical Nd-rich phase at both sides. Based on the analysis of phase diagrams, the formation mechanism is revealed from the following aspects: i) The amorphous formation ability of Nd-rich liquid phase in Ce magnet during sintering can be enhanced by introducing Pr-Nd-Al alloy; ii) The RE6(Fe, TM)11Al3 phase preferentially nucleates and grows during the process of cooling; iii) The interfacial tension among Nd-rich liquid phase, main phase and RE6(Fe, TM)11Al3 phase contributes to the formation of the sandwich-structure grain boundary. With the addition of Pr-Nd-Al alloy, the activity of Al entering the main phase is inhibited, resulting in almost no reduction of remanence and Curie temperature. The structural stability and decoupling effect of the sandwich-structure grain boundary phase are more conducive to the improvement of the coercivity and thermal stability of the Ce magnets. The coercivity of Ce magnet changes from 12.7 to 14.93 kOe (the increase extent is 17.6%). In the temperature range 20–100 ℃, the coercivity temperature coefficient varies from -0.767 to -0.680 %/℃ and the temperature stability obviously ameliorates about 11.3%.

Role of oxygen potential in dopant solubility in ferrite magnets: Enhanced Zn solubility and magnetization in La–Zn co-substituted magnetoplumbite-type strontium ferrite

To improve the performance of magnetoplumbite-type (M-type) AFe12O19 (A = Sr, Ba, Pb,…) hard ferrite magnets, such as the remanent magnetization and the coercivity, it is effective to dope transition metal elements at the Fe site. Substitution of nonmagnetic Zn, which preferentially occupies a minority-spin site in the ferrimagnets, is expected to increase magnetization. However, the solubility of Zn is limited to approximately 2–3% of Fe when synthesized in air. The solubility of divalent transition-metal substituents achieved by simultaneous substitution with trivalent cations on the A-site is often limited due to the auto reduction of Fe3+ to Fe2+. In this study, La–Zn co-substituted M-type strontium ferrites, Sr1−xLaxFe12−yZnyO19, were synthesized under different oxygen pressures of pO2 = 0.2, 1, and 10 atm, and the phase equilibrium and chemical composition were established by X-ray diffraction and wavelength dispersive X-ray spectroscopy. At pO2 = 10 atm, Sr-free La–Zn co-substituted ferrite, LaFe11.25Zn0.75O19, and single phases with actual compositions (x, y) = (0.42, 0.33) and (0.50, 0.45) were obtained for the first time. The single-phase samples exhibited a 5–9% higher saturation magnetization compared to non-doped SrFe12O19 at room temperature. Together with the coercivity enhancement by Co2+ substitution, oxygen potential control is a promising strategy to tune both coercivity and magnetization in future ferrite magnets.

Green synthesis of CoFe2O4/ZnS composite nanoparticles utilizing Moringa Oleifera for magnetic hyperthermia applications

The development of targeted cancer therapies is crucial to reducing harmful patient side effects. The incorporation of magnetic and fluorescent nanoparticles as heat mediators in magnetic hyperthermia is a novel and efficient strategy. This study investigated the potential of CoFe2O4/ZnS composite nanoparticles, successfully fabricated using a green synthesis method with Moringa oleifera leaf extract, as magnetic hyperthermia agents. X-ray diffraction spectra demonstrated the existence of the CoFe2O4 cubic spinel ferrite and ZnS cubic zinc-blend phases in the composite nanoparticles. The average particle sizes of CoFe2O4 and CoFe2O4/ZnS were 12 and 17 nm, respectively. The peak at 1406-1411 cm−1 indicated the incorporation of ZnS on the surfaces of the CoFe2O4/ZnS composite nanoparticles through the SO functional group. The UV–visible spectra showed that the bandgap increased from 3.7 to 4.5 eV with increasing ZnS content. Magnetic property studies indicated that the coercivity and saturation magnetization of the CoFe2O4/ZnS composite nanoparticles were lower than those of the CoFe2O4 nanoparticles but still showed ferromagnetic characteristics. Heating properties were investigated by measuring the specific absorption rate (SAR) in an alternating magnetic field at various ZnS contents. The SAR of the CoFe2O4 composite nanoparticles was 85.7 mW/g while that of the CoFe2O4/ZnS composite nanoparticles increased from 87.8 to 132.9 mW/g with increasing ZnS content. Results indicate that green-synthesized CoFe2O4/ZnS composite nanoparticles are promising candidates for magnetic hyperthermia applications in cancer therapy.