Magnetic-plasmonic nanocomposites combine magnetic and plasmonic functionalities within a single architecture, enabling enhanced thermo-responsive performance. In this work, magnetically hard CoFe2O4-Ag and magnetically soft Fe3O4-Ag nanocomposites were synthesized by thermal decomposition to investigate the structural, magnetic, plasmonic, and heating behaviors influenced by Ag nanoparticles. The magnetic particle sizes remained nearly constant (similar to 44 nm for CoFe2O4 and similar to 13 nm for Fe3O4) with increasing Ag content, while the Ag particle size evolved differently in the two systems. Raman and UV-Vis measurements confirmed the localized surface plasmon resonance of Ag. Increasing Ag concentration reduced the saturation magnetization in both systems; however, the coercivity remained stable in CoFe2O4-Ag but decreased in Fe3O4-Ag, where exchange bias was observed, indicating an interfacial magnetic coupling. Photothermal heating was evaluated under 532 nm laser irradiation (0.30 W cm(-2)), and magnetothermal performance was measured under an alternating magnetic field (H = 100 Oe, f = 450 kHz). For CoFe2O4-Ag, the applied field was much lower than the coercive field (H << Hc), restricting magnetization to minor hysteresis loops and limiting magnetic loss. In contrast, Fe3O4-Ag satisfied H <= Hc, enabling effective magnetization reversal and enhanced magnetothermal dissipation. Under dual excitation, Fe3O4-Ag exhibited nearly additive behavior, with the specific absorption rate approaching the sum of individual contributions. These results highlight the critical role of H/Hc matching and interfacial plasmonic effects in optimizing dual-mode nanoheaters.

MFe2O4 (M = Co and Mn) nanoparticles were synthesized from coconut coir extract using a microwave-assisted co-precipitation method, representing a green and sustainable approach for ferrite nanomaterial preparation. The physical properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, photoluminescence, Raman spectroscopy, and vibrating sample magnetometry. Scanning electron micrographs revealed nanoscale morphology with evidence of polymorphism. Rietveld refinement confirmed the formation of single-phase spinel ferrites with lattice constants ranging from 8.4224 & Aring; to 8.4782 & Aring; for CoFe2O4 and MnFe2O4, respectively. The distribution of metal cations at the tetrahedral and octahedral sites in the AB2O4 spinel lattice was found to depend on the synthesis route and significantly influenced the magnetic and optical behaviors of the materials. Raman spectra exhibited characteristic peaks corresponding to a mixed spinel structure. The optical band gaps estimated from the UV-vis spectra were 2.66 eV for CoFe2O4 and 2.64 eV for MnFe2O4. PL spectra showed four distinct emission peaks at 458, 692, 758, and 871 nm. Based on UV-vis and photoluminescence spectral results, a schematic energy band structure was constructed. Magnetic measurements, analyzed using the "law of approach" to saturation, revealed saturation magnetizations of 70 emu g-1 (CoFe2O4) and 49 emu g-1 (MnFe2O4) at 55 K-values that are among the highest reported for these systems; the squareness ratios were 0.58 and 0.12, respectively. The CoFe2O4 sample exhibited high effective anisotropy due to surface spin contributions, resulting in high coercivity and squareness. In contrast, the enhanced dipolar interactions in MnFe2O4 reduced coercivity and squareness. These magnetic behaviors were interpreted within the frameworks of the Stoner-Wohlfarth and superparamagnetic models that account for interparticle interactions.

This study presents a comprehensive investigation of the structure, morphology, and the optical and magnetic properties of manganese and cobalt ferrite nanoparticles synthesized via the co-precipitation method. Rietveld refinement confirmed the formation of a cubic spinel structure (space group Fd3m) in both samples and allowed for the estimation of Mn2+, Co2+, and Fe3+ ion distributions between tetrahedral and octahedral sites. Optical properties, including band gaps and Urbach energies, were derived from UV-Vis absorption spectra, enabling the determination of conduction and valence band edge positions. Magnetic measurements were analyzed using the law of approach to saturation, through which the saturation magnetization and magnetocrystalline anisotropy constant (K1) were extracted over a temperature range of 55-300 K. The temperature dependence of saturation magnetization (Ms) followed Bloch's law. At 55 K, the K1 values reached 1.58 x 106 erg/cm3 for CoFe2O4 and 1.41 x 106 erg/cm3 for MnFe2O4-both significantly higher than that of bulk Fe3O4. Interestingly, for CoFe2O4, the K1 exhibited a sixth-power dependence on saturation magnetization, consistent with theoretical expectations for multiaxial cubic-symmetry magnets. Conversely, for the MnFe2O4 sample, the K1 scaled with the Ms to the power of 1.16, indicating deviation from uniaxial behavior. Furthermore, the temperature dependence of K1 for CoFe2O4 and MnFe2O4 was well described by empirical expressions of the form K1 = K0 exp (- BT3/2), closely resembling trends observed in metallic magnets. These findings provide new insights into the structure-property in ferrite nanomaterials and their for-sensitive

The development of multifunctional nanomaterials capable of efficient and safe heat generation under clinically acceptable conditions is highly desirable for biomedical hyperthermia. Here, we report Fe3O4@TA-Fe3+ nanostructures, where TA denotes tannic acid, with tunable Fe3+/TA ratios (0.39-1.57), synthesized through a simple, green approach. Structural and morphological analyses (XRD, SEM, TEM) confirmed spherical Fe3O4 cores (-14 nm) uniformly coated by tannic acid-Fe3+ complexes, which stabilized the surface and promoted clustering with hydrodynamic diameters of -260 nm. Heating performance was systematically evaluated under near-infrared laser irradiation, alternating magnetic field exposure, and their combined application. Fe3O4@TA-Fe3+ exhibited consistently higher SAR values than bare Fe3O4, evidencing the synergistic role of the photothermal polymer coating. Under biomedical limit conditions (AMF: 150 Oe, 340 kHz; laser: 808 nm, 0.3 W/cm2), dual-mode operation enhanced SAR by 140-310 % relative to single modalities. These results underscore the potential of Fe3O4@TA-Fe3+ nanostructures as safe, efficient, and biocompatible platforms for magnetic-photothermal hyperthermia.

Nd0.6Sr0.4Mn1-yCoyO3 (y = 0-0.09) compounds have been fabricated by using solid-state reactions. X-ray diffraction analyses reveal their monophase in the Imma orthorhombic structure. When y increases, there are gradual reductions of the unit-cell parameters and porosity. Concurrently, the Curie temperature (T-C) also reduces from 280 K (y = 0) to similar to 232 K (y = 0.09). In the vicinity of T-C, we have observed the Griffiths phase that more develops as increasing y. The presence of this phase enhances magnetocaloric responses, corresponding to the operating range widened above 95 % and the cooling power enhanced similar to 30 % for an applied field H = 30 kOe. All materials exhibit the characters of a second-order phase transition with a narrow hysteresis loop, suggesting their applicability in magnetic cooling devices operating below room temperature. A coexistence of Mn-3+,Mn-4+ and Co-3+,Co-4+ ions is thought to establish randomly competing ferromagnetic and antiferromagnetic interactions in Nd0.6Sr0.4Mn1-yCoyO3 compounds that widen the Griffiths phase, short-range magnetic ordering, and magnetocaloric response.

Magnetic nanoparticles (NPs) are promising agents for magnetic hyperthermia (MH) due to their ability to convert electromagnetic energy into heat. Their high stability in solution, which is essential to prevent aggregation and ensure uniform distribution as well as their high specific absorption rate (SAR) and intrinsic loss power (ILP) values are especially important in magnetic hyperthermia. This study explores how doping iron oxide NPs with zinc and surface functionalizing them with polyvinylpyrrolidone (PVP) affects their magnetic and heating properties. The saturation magnetization (MS) of ZnxFe3-xO4 NPs at 50 K increases from 76 to 93.5 emu/g corresponding with increasing Zn content from x = 0 up to 0.20, and conversely their coercivity (HC) decreases from 135 down to 77 Oe. For PVP coated NPs, MS is reduced by the presence of nonmagnetic PVP, whereas their HC is increased due to reduced interparticle interactions. Furthermore, the high stability of PVP coated Zn 0.20 Fe 2.80 O 4 NPs in solution is confirmed by the Zeta potential of 46 mV. Notable, high SAR of 460 W/g and ILP of 4.04 nH m2/kg values make them potential candidates for MH applications.

In present work, Gd-doped CoFe2O4 nanoparticles (CoGdxFe2-xO4, x = 0.00, 0.05, 0.15, and 0.25) have been successfully prepared to evaluate the impact of cation distribution on magnetic properties and the samples' application efficiency in Hyperthermia and Magnetic Resonance Imaging. The replacement of Fe3+ ions in CoFe2O4 nanoparticles by Gd3+ ions causes a reduction in structural parameters (size, density, and lattice parameter). Considering X-ray diffraction data in detail has suggested a new way to determine Gd3+ ion's content at tetrahedral and octahedral sites. The change in saturation magnetization and magnetic anisotropy in doped samples is explained based on cation distribution. In particular, high magnetic properties for CoGd0.15Fe1.85O4 sample (54.4 emu/g of saturation magnetization and 46.3 kJ/m3) is related to 0.042 and 1.08 of the Gd3+ ions content in at tetrahedral and octahedral sites, respectively. Accordingly, this sample has the highest specific absorption rate (95.1 W/g). Especially, this sample's relaxivity (6.24 mM-1s-1 of longitudinal relaxivity and 78.06 mM- 1s- 1 of transverse relaxivity) also reveals that CoGd0.15Fe1.85O4 nanoparticles can be used as a dual contrast agent. All results claim that Gd-doped CoFe2O4 NPs can become a novel multifunctional material applied simultaneously in Hyperthermia and Magnetic Resonance Imaging.

MFe 2 O 4 (M = Co and Mn) nanoparticles were synthesized from coconut coir extract using a microwave-assisted co-precipitation method, representing a green and sustainable approach for ferrite nanomaterial preparation.

In this report, we present results on the multiferroic properties of four nanocomposite samples of NiFe2O4-Ba0.7Ca0.3TiO3 (NFO/BCTO), which were fabricated through combinations of high-energy ball milling, heat treatment, and spark plasma sintering techniques. Structural analyses revealed that these samples simultaneously contain two phases of nano-sized NiFe2O4 (NFO) and Ba0.7Ca0.3TiO3 (BCTO) crystals. The addition of NFO into the BCTO-host did not alter the crystal structure but significantly improved the multiferroic characteristics compared to pure BCTO. Furthermore, variations in saturation magnetization (M-s) and coercivity (H-c) were investigated as a function of temperature. The results showed that Ms increased gradually with the concentration of NFO. In terms of temperature dependence, M-s(T) data deviated from the Bloch's law with an exponent coefficient alpha changing in the range of 1.8-1.9, decreasing gradually as the NFO concentration increased. Meanwhile, H-c decreased gradually as the NFO concentration increased and followed the Kneller's law in terms of temperature dependence.

Các hệ hạt nano tổ hợp hai thành phần hiện đang được nghiên cứu và phát triển tại nhiều phòng thí nghiệm nhờ vào những tiến bộ trong tổng hợp hóa học. Vật liệu nano tổ hợp hai thành phần nền Fe3O4 dạng lõi-vỏ đã cho thấy sự cải thiện về một số tính chất so với các thành phần vật liệu đơn lẻ. Trong nghiên cứu này, vật liệu nano tổ hợp từ tính hai thành phần Fe3O4 và CoFe2O4 với các độ dày vỏ khác nhau đã được tổng hợp bằng phương pháp phát triển hạt kết hợp phân hủy nhiệt. Kết quả từ giản đồ nhiễu xạ tia X (XRD) và ảnh hiển vi điện tử quét truyền qua kết hợp phổ tán xạ năng lượng tia X dạng bản đồ (STEM-EDX Mapping) cho thấy các mẫu nano tổ hợp đã được hình thành với cấu trúc hình thái học dạng lõi-vỏ Fe3O4@CoFe2O4. Kích thước hạt lõi Fe3O4 khoảng 18 nm và độ dày vỏ CoFe2O4 thay đổi từ 2-9 nm. Phép đo từ độ, được thực hiện trên hệ từ kế mẫu rung (VSM) với hai cách chuẩn bị mẫu khác nhau là nén bột bình thường và ghim hạt trong nền sáp, cho thấy có sự ảnh hưởng của cả tương tác giữa các hạt và tương tác nội hạt giữa lớp lõi Fe3O4 và vỏ CoFe2O4 lên tính chất từ. Bên cạnh đó, các kết quả đo từ cũng cho thấy tính chất từ bị ảnh hưởng bởi độ dày lớp vỏ CoFe2O4.

MFe2O4 (M = Co, Fe, Mn, Zn) nanoparticles were successfully synthesized by coprecipitation. Analyzing the X-ray diffraction by the Rietveld method confirmed the spinel ferrite structure of the samples. Rietveld refinement results show that Co, Mn and Zn occupy both the tetrahedral and octahedral sites. Variation in elastic parameters was determined by Fourier transform infrared spectroscopy, and cation distribution was deduced from X-ray diffraction. X-ray diffraction peak expansion was analyzed by employing a variety of calculating methods such as modified Scherrer, Williamson–Hall, size–strain, and Halder–Wagner to determine the crystallite size and elastic parameters of the cubic-structured MFe2O4 nanoparticles, including intrinsic strain, stress, and energy density. Comparison of the results obtained from these different methods revealed that they are ideally suited to each other. Moreover, the transmission electron microscopy image confirmed that the average size of MFe2O4 (M = Co, Fe, Mn, Zn) nanoparticles ranges from 10 to 14nm, consistent with the dimensions obtained from the preceding methods.

It has been known that a La2/3Ca1/3MnO3 (LMO) bulk sample has the maximum magnetic entropy change (|Delta S-max|) larger than |Delta S-max| of Gd - a conventional magnetocaloric (MC) material. However, such large change just takes place in a narrow range of temperature because of its first-order character. This influences the working temperature range (Delta T) and relative cooling power (RCP) of LMO. Previous works have revealed that the fabrication of LMO nanoparticles with the second-order character would improve the magnitude of Delta T and RCP, and reduce magnetic hysteresis losses. In this work, we suggest that the combination of LMO nanoparticles (NPs) with Gd powder as nanocomposites (NCPs), termed (100-x)LMO + xGd with x = 50 and 75 wt%, further enhances Delta T from 60 to similar to 94 K (in the range T = 220-314 K) for applied fields H = 5-20 kOe. These values are larger than those of initial materials Gd and LMO NPs (Delta T approximate to 40 K), reported composites (Delta T < 50 K), and even the composites fabricated from a LMO bulk and Gd powder (Delta T < 60 K) in the same fields. Additionally, all NCPs exhibit the second-order character, and RCP of optimal NCPs is nearly comparable to that of Gd. These features demonstrate application potentials of NCPs for conventional refrigerators operating in a large temperature range.

Co n-1TMO n-2 + (n = 6-8), (TM = V, Cr, Mn, and Fe) clusters are investigated using density functional theory calculations. The transition metal atoms preferentially replace one Co atom at sites where the number of metal-oxygen bonds is maximized, forming more stable structures. The evaporation of a Co atom is the most fragile dissociation channel for both pure and doped species. Bare cobalt oxide clusters exhibit parallel spin ordering, whereas both parallel and antiparallel spin ordering are observed in the doped species. Notably, a ferromagnetic-to-ferrimagnetic transition occurs in the V-doped clusters, while the ferromagnetic behavior is enhanced in the Fe-doped species.

MFe2O4 (M = Co, Fe, Mn) nanoparticles were successfully formed through the chemical co-precipitation technique. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis were used to investigate samples' structural properties. The investigated structural properties included phases formed, crystallite size, cation distribution, hopping length, bond length, bond angle, edge length, and shared and unshared octahedral edge length. Scanning electron micrographs of the prepared samples demonstrated well-defined crystalline nanoparticles. The grain diameter was 15, 9, and 34 nm for CoFe2O4, Fe3O4, and MnFe2O4, respectively. The energy-dispersive X-ray analysis confirmed the existence of every element (Co, Fe, and O) and no discernible impurities in the samples. The optical properties were studied in detail through photoluminescence (PL) spectroscopy and Raman spectroscopy. The presence of active modes in Raman spectra confirmed the spinel structure of the MFe2O4 nanoparticles. The direct bandgap energy estimated through UV-visible spectroscopy was about 2.59-2.64 eV, corresponding with the energy-band structures of the octahedral site (1.70 eV) and the tetrahedral site (0.9 eV). This result was further confirmed by PL emission spectra. Based on Mie theory and UV-visible and PL spectral data, the mechanism of photothermal characterization for MFe2O4 nanoparticles was determined. Investigating the changes in temperature of magnetic parameters including coercivity, squareness ratio, and saturation magnetization for MFe2O4 samples showed the dominant influence of ion distribution and A-A, A-B, and B-B exchange interactions. This study also showed that strong anisotropy and weak dipolar interaction tended to increase the coercivity and squareness ratio of CoFe2O4. Conversely, weaker anisotropy and stronger dipolar interaction corresponded with the small coercivity and squareness ratio of Fe3O4 and MnFe2O4 samples.

Ceramic compounds BaTi1-xFexO with x = 0-0.2 prepared by solid state reaction technique were studied using Xray diffraction, Raman spectroscopy, and magnetometry methods focusing on the correlation between the structure and magnetic properties. Chemical doping with Fe ions leads to a concentration driven structural transformation from the single phase tetragonal (T-) structure to the hexagonal (H-) structure with a mixed structural state stable in the concentration range 0.06 < x <= 0.2. Increase in the Fe ions content causes a stabilization of weak ferromagnetic state driven by the exchange interactions Fe3+ - O - Fe3+ ions strongly dependent on the structural positions of the Fe ions. Increase of the dopant content above x = 0.08 leads to a decrease of the remnant magnetization which is mainly caused by a stabilization of Fe4+ ions as well as by the lattice defects associated with oxygen vacancies formed to keep electroneutrality of the compounds. The results of the structural and magnetization measurements allowed to itemize the type of exchange interactions between Fe ions residing different structural positions of the hexagonal lattice as well as to reveal structural instability of the T- and H- phases under ambient conditions and applied electric field which shows a possibility to control the structure and magnetic properties of the mixed compounds via external stimuli.

In this study, we developed a non-enzymatic electrochemical sensor using a porous graphene electrode modified with ZnO nanoparticles (ZnO/fPGE sensor) to determine xanthine (XA) content. The ZnO/fPGE sensor is fabricated using a hydrothermal method and CO2 infrared laser writing technique on a polyimide film. The morphology, structure, and properties of the ZnO/fPGE were meticulously characterized using Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and Von-Ampe spectroscopy methods. The ZnO/fPGE sensor exhibited a broad linear response range from 1 µM to 100 µM, a low limit of detection (LOD) of 0.29 µM, high sensitivity at 7.05 µA.µM⁻¹.cm⁻², and demonstrated effective resistance to common interferences such as uric acid, ascorbic acid, dopamine, glucose, and xanthine. Notably, the ZnO/fPGE sensor has created a conducive electrical environment for the advancement of high-performance electrochemical biosensors, specifically for the precise determination of xanthine levels in meat and fish products.

Trong bối cảnh toàn cầu đang đối diện với nhiều thách thức về cung cấp năng lượng và tác động nghiêm trọng của biến đổi khí hậu, năng lượng hydro được xem là một trong những lựa chọn quan trọng nhất để thay thế năng lượng hóa thạch và đóng góp vào mục tiêu phát triển năng lượng sạch và bền vững. Phản ứng tách nước là một quá trình quan trọng để sản xuất hydro thông qua thu thập và tách khí hydrogen từ nước. Điều này đòi hỏi sự hiện diện của chất xúc tác có hiệu suất cao, có khả năng tăng tốc độ phản ứng và đảm bảo tính bền vững trong quá trình hoạt động. Điểm mấu chốt của việc nghiên cứu và phát triển vật liệu xúc tác là để tối ưu hóa hiệu suất và giảm chi phí sản xuất hydro. Trong báo cáo này, chúng tôi trình bày một số những tiến bộ về tổng hợp chế tạo vật liệu xúc tác quang điện hóa cho phản ứng tách nước dạng oxit.

Fe3O4/CoFe2O4 core/shell nanoparticles with varying shell thickness were fabricated by seed-mediated growth via thermal decomposition method. Ligand exchange process using poly(maleic anhydride-alt-1-octadecene) (PMAO) was performed to prepare the aqueous magnetic fluids from the as-synthesised nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Quantum Design PPMS VersaLab were utilised to characterise morphological and magnetic properties of the sample. XRD results showed that all the particles were single phase with spinel structure and the average crystallite size in the range of 11-17 nm. All particles were spherical in TEM images with similar size compared to results calculated from XRD. Magnetic measurements were performed at different temperatures (50 - 300 K) at 30 kOe. The result showed that the saturation magnetisation (M-s) and coercivity (H-C) were significantly increased with the formation of hard magnetic shell with varying thickness. The dynamic light scattering (DLS) analysis presented a narrow distribution and zeta potential of -16 to -35 mV, indicating a good stability of the ferrofluids. The cytotoxicity of the FOC3/PMAO ferrofluid, which has the highest SAR value of 372.02 W g(-1), was tested on Hep-G2 cell line at different concentrations from 10 to 100 mu g ml(-1). Less than 30% of the cell was inhibited, indicating that the FOC3/PMAO particles have low toxicity at these tested concentrations. Thus, these as-synthesised core/shell nanoparticles with uniform particle size, high saturation magnetisation, good stability and five-time increased specific absorption rate (SAR) compared to the Fe3O4 core nanoparticles are very promising in hyperthermia and magnetic resonance imaging (MRI) applications.

Designing and fabricating microwave-absorbing materials (MAMs) with a widening effective absorption bandwidth, intense reflection loss, thin matching thickness, and lightweightness is an effective method to mitigate the drawbacks of electromagnetic (EM) radiation while enjoying its advantages for modern life. Among MAMs, composites of magnetic materials and dielectric materials could be the best candidates. CoFe2O4 (CFO), with its unique crystalline structure, excellent EM properties, and environmentally friendly and low-cost production, has been extensively used as MAM. Meanwhile, carbonaceous-based materials have also been used as MAMs due to their intriguing properties, including flexibility, lightweight, and suitable dielectric properties. Therefore, composites of CFO/carbonaceous-based materials could be among the best MAMs. This review will be systematically reviewed for MAMs of CFO/carbonaceous-based materials in the form of two, three, and four components. The principal microwave loss mechanism for attenuation mechanisms will be carefully examined. This review also summarized perspectives and challenges for the future of CFO/carbonaceous-based materials for human security, interference protection, and radar signal absorption.