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The magnetocaloric effect (MCE) is currently intensively investigated in various rare earths (RE)-containing magnetic solids, not only for developing appropriate magnetocaloric materials (MCMs) for cryogenic magnetic cooling but also for deepening our understanding into the inherent physical properties of these materials. Here, we provide a systematic experimental investigation into a series of new RE2CuTiO6 (RE = Dy, Ho, Er) double-perovskite (DP) oxides regarding the structural and magnetic properties, especially for their cryogenic MCE and magnetic-phase transition (MPT). All of these RE2CuTiO6 oxides crystallize in a B-site-ordered hexagonal DP-type structure with the symmetry of the crystallographic space group P6̅m2. These DP oxides exhibit magnetic ordering, with MPT temperatures of approximately 2.7, 2.2, and 2.7 K for Dy2CuTiO6, Ho2CuTiO6, and Er2CuTiO6, respectively. The magnetocaloric performances of the RE2CuTiO6 DP oxides were characterized by the peak values of magnetic entropy change, the temperature-averaged magnetic entropy change (5K-lift), and relative cooling powers. These magnetocaloric parameters were deduced to be 18.7/17.9 J/kgK and 298.2 J/kg for Dy2CuTiO6, 12.5/12.2 J/kgK and 273.9 J/kg for Ho2CuTiO6, and 13.8/12.9 J/kgK and 188.4 J/kg for Er2CuTiO6 under a magnetic field change of 0-5 T. These values are comparable to those of most reported RE-containing magnetocaloric materials, indicating that these RE2CuTiO6 DP oxides are promising candidates for cryogenic magnetic cooling applications.

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Organic-inorganic hybrid crystals have diverse functionalities, for example in energy storage and luminescence, due to their versatile structures. The synthesis and structural characterization of a new cobalt-vanadium-containing compound, 2[Co(en)3]3+(V4O13)6-·4H2O (1) is presented. The crystal structure of 1, consisting of [Co(en)3]3+ complexes and chains of corner-sharing (VO4) tetrahedra, was solved by single-crystal X-ray diffraction in the centrosymmetric space group P1. Phase purity of the bulk material was confirmed by infrared spectroscopy, scanning electron microscopy, elemental analysis and powder X-ray diffraction. The volume expansion of 1 was found to be close to 1% in the reported temperature range from 100 to 300 K, with a volume thermal expansion coefficient of 56 (2) × 10-6 K-1. The electronic band gap of 1 is 2.30 (1) eV, and magnetic susceptibility measurements showed that the compound exhibits a weak paramagnetic response down to 1.8 K, probably due to minor CoII impurities (<1%) on the CoIII site.

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CONTEXT: Nowadays, Perovskite materials with diverse compositions and structures have garnered significant attention for their potential applications across various industrial and technological fields. Here, we investigated the structural, electronic, optical, thermodynamic, thermoelectric, and magnetic properties of perovskite PrFeO3 using density functional theory and Monte Carlo simulations. The optimization results demonstrate that the ferromagnetic phase is more stable than the antiferromagnetic phase. Under the GGA + SOC + U and GGA + mBJ approaches, the electronic results of the PrFeO3 compound expose the half-metallic and magnetic behavior. It was also demonstrated that introducing dilatation strain can effectively enhance both the mechanical and thermal stability of PrFeO3. Additionally, the optical properties show that this material has potential uses for solar cells because of its capacity to absorb light in the ultraviolet (UV) spectrum. The maximum values of the Seebeck coefficient reach 90 µV/K at 1000 K, indicating the potential of PrFeO3 as an efficient thermoelectric material. The magnetic properties exhibit a first transition of spin reorientation (TSR) at 171.44 K, followed by a second-order transition at 707.15 K. This investigation provides valuable insights into the unstudied aspect of Perovskite PrFeO3. METHODS: To carry out this investigation, we employed the density functional theory (DFT) implemented in the Wien2k package. To determine the exchange-correlation potential, we utilized the GGA-PBE (Perdew, Burke, and Ernzerhof) approach. The SOC was included based on the second-variational method using scalar relativistic wavefunctions, and electron-electron Coulomb interactions for Fe and Pr are considered in the rotationally invariant way GGA + SOC + U. In this paper, the effective parameter Ueff = U - J was adopted, where U and J stand for the Coulomb and exchange parameters, respectively. Also, we opted for the modified Becke-Johnson potential (mBJ) for comparison. The thermodynamic properties are obtained using the quasi-harmonic Debye model via Gibbs2 software programs. For the calculation of thermoelectric coefficients, a combination of first-principles band structure calculations and the Boltzmann transport theory within the rigid band approximation (RBA) and the constant scattering time approximation (CSTA) was employed, utilizing the BoltzTrap code. Subsequently, we delve into the magneto-caloric and magnetic properties by employing Monte Carlo simulations.

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The emergence of π-magnetism in low-dimensional carbon-based nanostructures, such as nanographenes (NGs), has captured significant attention due to their unique properties and potential applications in spintronics and quantum technologies. Recent advancements in on-surface synthesis under ultra-high vacuum conditions have enabled the atomically precise engineering of these nanostructures, effectively overcoming the challenges posed by their inherent strong chemical reactivity. This review highlights the essential concepts and synthesis methodologies used in studying NGs. It also outlines the remarkable progress made in understanding and controlling their magnetic properties. Advanced characterization techniques, such as scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM), have been instrumental in visualizing and manipulating these nanostructures, which highlighting their critical role in the field. The review underscores the versatility of carbon-based π-magnetic materials and their potential for integration into next-generation electronic devices. It also outlines future research directions aimed at optimizing their synthesis and exploring applications in cutting-edge technologies.

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The SrFeO3 nanoparticles doped with 5% and 10% Gd were synthesized using the solution combustion method. The phase formation of the synthesized nanoparticles was confirmed by powder XRD analysis. FESEM and HRTEM were employed to examine the morphology of the samples, revealing well-ordered, agglomerated nanoparticles. EDAX analysis was conducted on all samples, confirming the presence of the desired elements. X-ray photoelectron spectroscopy confirmed the presence of mixed oxidation states of Fe3+ and Fe4+. Magnetization studies, performed using a SQUID magnetometer, showed ferromagnetic behaviour in all samples, with a significant increase in magnetic moment observed with higher Gd doping. The enhanced magnetic moments and reduced coercivity in Gd-doped SrFeO3 suggest that these materials could be suitable for spintronic applications.

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In this study, Zn-Al ferrite/polypyrrole (PPy) nanocomposites were synthesized and thoroughly characterized to explore their potential for microwave applications. X-ray diffraction analysis confirmed the presence of ZnO, AlFeO3, and Fe2O3 phases, with the crystal size decreasing from 31 nm to 19.6 nm as aluminum content increased. High-resolution transmission electron microscopy (HR-TEM) revealed a distinctive core-shell morphology, where the polypyrrole encapsulates the ZnAlxFe2-xO4 particles. Magnetic measurements showed that decreasing aluminum concentration led to a reduction in both saturation magnetization (Ms) from 75 emu/g to 36 emu/g and remanent magnetization (Mr) from 2.26 emu/g to 2.00 emu/g. Dielectric analysis indicated that both the real (ε') and imaginary (ε″) components of dielectric permittivity decreased with increasing frequency, particularly between 10 and 14 GHz. Furthermore, electrical modulus analysis highlighted the significant impact of aluminum doping on relaxation time (τIP), indicating the presence of interface polarization. Impedance spectroscopy results underscored the dominance of interface polarization at lower frequencies and the presence of strong conduction paths at higher frequencies. These combined magnetic and dielectric loss mechanisms suggest that the Zn-Al ferrite/polypyrrole nanocomposite is a promising candidate for advanced microwave absorption applications.

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In the present paper, we present an electron magnetic resonance (EMR) study of Ni50.2Mn28.3Ga21.5 powders obtained from melt-spun ribbons in the milling process. We registered EMR spectra in various temperatures at the X-band. In the EMR spectra recorded for the samples taken at the beginning of the milling process, the "training effect" was observed. After 2 h of milling, this phenomenon was no longer observed. To determine the basic EMR parameters, such as linewidth, resonance field, and asymmetry parameters, the experimental data were fitted using a single metallic Lorentz line. In high-temperature regions, we observed the influence of dispersion on the shape of the spectra, but as the temperature decreased, the asymmetry of line was reduced. The shift in the resonance field value at high temperatures and the temperature dependence of the linewidth below Curie temperature indicate that the investigated samples exhibited a characteristics of a spin-glass alloy.

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To improve the magnetic properties of iron-based soft magnetic composites (SMCs), polytetrafluoroethylene (PTFE) with excellent heat resistance, electrical insulation, and extremely high electrical resistivity was chosen as an insulating coating material for the preparation of iron-based SMCs. The effects of PTFE content, compaction pressure, and annealing treatment on the magnetic properties of Fe/PTFE SMCs were investigated in detail. The results demonstrate that the PTFE insulating layer is successfully coated on the surface of iron powders, which effectively reduces the core loss, increases the resistivity, and improves the frequency stability and the quality factor. Under the combined effect of optimal PTFE content, compaction pressure, and annealing treatment, the iron-based SMCs exhibit a high effective permeability of 56, high saturation magnetization of 192.9 emu/g, and low total core losses of 355 mW/cm3 and 1705 mW/cm3 at 50 kHz for Bm = 50 mT and 100 mT. This work provides a novel insulating coating layer that optimizes magnetic properties and is advantageous for the development of iron-based SMCs. In addition, it also provides a comprehensive understanding of the relationship between process parameters and magnetic properties, which is of great guiding significance for scientific research and industrial production.

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The present study explores the synthesis and bio-safety evaluation of gadolinium-doped carbon quantum dots (GCQDs) as a potential dual-contrast agent for diagnostic imaging. GCQDs exhibit both fluorescent and magnetic properties, making them suitable for UV-Vis and magnetic resonance imaging (MRI). The synthesis of GCQDs was achieved via hydrothermal treatment, incorporating gadolinium into the carbon quantum dot matrix. The magnetic properties of GCQDs were analyzed, showing significantly enhanced values compared to gadobutrol, a common MRI contrast agent. However, synthesis constraints limit the gadolinium content achievable in nanodots. To assess the safety of GCQDs, their effects on the embryonic development of zebrafish (Danio rerio) were examined. Various concentrations of GCQDs were tested, observing mortality rates, hatchability, malformations, heartbeats, spontaneous movement, and GCQDs uptake. Dialysis studies indicated that gadolinium ions are incorporated into the internal structure of the carbon nanodots. Zebrafish toxicity tests revealed that while survival rates were comparable to control groups, hatchability decreased significantly with higher gadolinium concentrations in GCQDs. Fluorescence microscopy showed no statistical differences in the fluorescence intensity between groups. These findings suggest that GCQDs could serve as an effective dual-contrast agent, combining the optical imaging capabilities of CQDs with the enhanced MRI contrast provided by gadolinium. This study underscores the need for further research on the synthesis methods and biological interactions of GCQDs to ensure their safety and efficacy in medical applications.

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Although chromium trihalides are widely regarded as a promising class of two-dimensional magnets for next-generation devices, an accurate description of their electronic structure and magnetic interactions has proven challenging to achieve. Here, we quantify electronic excitations and spin interactions in CrX 3 (X = Cl, Br, I) using embedded many-body wavefunction calculations and fully generalized spin Hamiltonians. We find that the three trihalides feature comparable d-shell excitations, consisting of a high-spin 4 A 2 ( t 2 g 3 e g 0 ) ground state lying 1.5-1.7 eV below the first excited state 4 T 2 ( t 2 g 2 e g 1 ). CrCl3 exhibits a single-ion anisotropy A sia = - 0.02 meV, while the Cr spin-3/2 moments are ferromagnetically coupled through bilinear and biquadratic exchange interactions of J 1 = - 0.97 meV and J 2 = - 0.05 meV, respectively. The corresponding values for CrBr3 and CrI3 increase to A sia = -0.08 meV and A sia= - 0.12 meV for the single-ion anisotropy, J 1 = -1.21 meV, J 2 = -0.05 meV and J 1 = -1.38 meV, J 2 = -0.06 meV for the exchange couplings, respectively. We find that the overall magnetic anisotropy is defined by the interplay between A sia and A dip due to magnetic dipole-dipole interaction that favors in-plane orientation of magnetic moments in ferromagnetic monolayers and bulk layered magnets. The competition between the two contributions sets CrCl3 and CrI3 as the easy-plane (A sia + A dip >0) and easy-axis (A sia + A dip <0) ferromagnets, respectively. The differences between the magnets trace back to the atomic radii of the halogen ligands and the magnitude of spin-orbit coupling. Our findings are in excellent agreement with recent experiments, thus providing reference values for the fundamental interactions in chromium trihalides.

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Herein, the standard solid-state reaction process was employed to synthesize the polycrystalline Ba1-xDy2x/3Ti0.98Mn0.02O3 (x = 0.0000-0.0085) ceramics and each composition was sintered at 1200 °C for 3 h. The structural, morphological, electrical, and magnetic properties were carried out by the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), impedance analyzer, and vibrating sample magnetometer (VSM) to investigate the influence of doping of Dy 3+ (low concentration) and Mn4+ in BaTiO3 simultaneously. The XRD study confirmed the formation of perovskite structure with tetragonal symmetry of the prepared solid solution. The magnitude of the porosity (P%) decreased from 13.22 to 9.49 with increasing content of Dy and x = 0.0080 sample showed the lowest value. The mean grain size was estimated in the micrometer range, with values ranging from 0.5713 to 0.1457 µm. The highest grain size determined for the x = 0.0070 sample was 0.5713 µm. The Brunauer-Emmett-Teller (BET) adsorption isotherm measurements were used to estimate the specific surface area; the result was 24.181 m2/g for x = 0.007 composition. For the compound with x = 0.0070 the maximum recorded dielectric constant was found to be 6 × 103 at 103 Hz. A relatively lower dielectric loss (<5 %) was observed. The Nyquist plot illustrated that only the grain boundary effect is significant for the conduction process in the studied compositions. The present solid solution revealed better magnetic results compared to other reported ceramics similar to the prepared constituents. The optimum value of saturation magnetization (0.371 emu/g) was obtained for x = 0.0080 composition. Among the synthesized Dy doped samples x = 0.0075 composition displayed a significant complex initial permeability ( µ i / ). An enhanced relative quality factor (RQF) was seen with increasing frequency and the highest relative quality factor was noticed (>100) for the x = 0.0075 sample at 108 Hz. The studied materials could be employed as an environmentally acceptable alternative to the hazardous lead (Pb)-based multiferroic substance.

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The chromium crystal doped with119Sn isotope was studied using the nuclear resonance inelastic x-ray scattering and first principles calculations. The Sn partial phonon density of states (PDOS) was obtained for three temperatures that correspond to different magnetic states of Cr. At all temperatures, the energy spectrum consists of a broad band around 18 meV and a narrow peak at 43 meV. The additional peak around 39 meV is observed only in the magnetically ordered phases, indicating the influence of magnetic order in chromium on lattice dynamics. The partial PDOS calculated with the antiferromagnetic order on Cr atoms show a very good agreement with the experimental data. It is revealed that the high-energy peak is lying above the phonon spectra of the pure bcc-Cr crystal. These are the local modes with the increased energies due to a strongly reduced distance between Sn and the nearest-neighbor Cr atoms.

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Anisotropic bulk magnets of ThMn12-type SmFe10V2 with a high coercivity (Hc) were successfully fabricated. Powders with varying particle sizes were prepared using the ball milling process, where the particle size was controlled with milling time. A decrease in Hc occurred in the heat-treated bulk pressed from large-sized powders, while heavy oxidation excessively occurred in small powders, leading to the decomposition of the SmFe10V2 (1-12) phase. The highest Hc of 8.9 kOe was achieved with powders ball-milled for 5 h due to the formation of the grain boundary phase. To improve the maximum energy product ((BH)max), which is only 2.15 MGOe in the isotropic bulk, anisotropic bulks were prepared using the same powders. The easy alignment direction, confirmed by XRD and EBSD measurements, was <002>. Significant enhancements were observed, with saturation magnetization (Ms) increasing from 59 to 79 emu/g and a remanence ratio (Mr/Ms) of 83.7%. (BH)max reaching 7.85 MGOe. For further improvement of magnetic properties, controlling oxidation is essential to form a uniform grain boundary phase and achieve perfect alignment with small grain size.

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New cobalt(II)-based complexes with [N2O2] coordination formed by two bis-chelate ligands were synthesized and characterized by a multi-technique approach. The complexes possess an easy-axis anisotropy (D < 0) and magnetic measurements show a field-induced slow relaxation of magnetization. The spin-reversal barriers, i.e., the splitting of the two lowest Kramers doublets (UZFS), have been measured by THz-EPR spectroscopy, which allows to distinguish the two crystallographically independent species present in one of the complexes. Based on these experimental UZFS energies together with those for related complexes reported in literature, it was possible to establish magneto-structural correlations. UZFS linearly depends on the elongation parameter εT of the (pseudo-)tetrahedral coordination, which is given by the ratio between the average obtuse and acute angles at the cobalt(II) ion, while UZFS was found to be virtually independent of the twist angle of the chelate planes. With increasing deviation from the orthogonality of the latter, the rhombicity (|E/D|) increases.

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The interaction of magnetic order and spontaneous polarization is a fundamental coupling with the prospect for the control of electronic properties and magnetism. The connection among magnetic order, charge localization and associated metal-insulator transition (MIT) are cornerstones for materials control. Materials that combine both effects are therefore of great interest for testing models that claim the occurrence of spontaneous polarization from magnetic and charge order. One class of materials proposed to combine these functionalities is the family of RNiO3 (R: Lanthanide or Yttrium), whose members show a clear MIT and an antiferromagnetic ground state and for which an electric polarization has been predicted. Here, using resonant magnetic x-ray scattering with circular polarization and an applied electric field we show that YNiO3 possess a magnetic structure containing domains of spin-rotations that are consistent with an electric polarization. We show a reversal of the magnetic structure with the applied electric field confirming that charge ordered RNiO3 are magnetoelectric type II multiferroics with a MIT.

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Recently, MnTe was established as an altermagnetic material that hosts spin-polarized electronic bands as well as anomalous transport effects like the anomalous Hall effect. In addition to these effects arising from altermagnetism, MnTe also hosts other magnetoresistance effects. Here, we study the manipulation of the magnetic order by an applied magnetic field and its impact on the electrical resistivity. In particular, we establish which components of anisotropic magnetoresistance are present when the magnetic order is rotated within the hexagonal basal plane. Our experimental results, which are in agreement with our symmetry analysis of the magnetotransport components, showcase the existence of an anisotropic magnetoresistance linked to both the relative orientation of current and magnetic order, as well as crystal and magnetic order. Altermagnetism is manifested as a three-fold component in the transverse magnetoresistance which arises due to the anomalous Hall effect.

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The magnetic properties of Aurivillius-phase Bi7Fe3Ti3O21 (BFT) and Bi7-xGdxFe3Ti3O21, where x = 0.2, 0.4, and 0.6 (BGFT), were investigated. Ceramic material undoped (BGF) and doped with Gd3+ ions were prepared by conventional solid-state reaction. In order to confirm that the obtained materials belong to Aurivillius structures, XRD tests were performed. The XRD results confirmed that both the undoped and the gadolinium-doped materials belong to the Aurivillius phases. The qualitative chemical composition of the obtained materials was confirmed based on EDS tests. The temperature dependences of magnetization and magnetic susceptibility were examined for the ceramic material both undoped and doped with Gd3+ ions. The measurements were taken in the temperature range from T = 10 K to T = 300 K. Using Curie's law, the value of the Curie constant was determined, and on its basis, the number of iron ions that take part in magnetic processes was calculated. The value of Curie constant C = 0.266 K, while the concentration of iron ions Fe3+, which influence the magnetic properties of the material, is equal 3.7 mol% (for BFT). Hysteresis loop measurements were also performed at temperatures of T = 10 K, T = 77 K, and T = 300 K. The dependence of magnetization on the magnetic field was described by the Brillouin function, and on its basis, the concentration of Fe3+ ions, which are involved in magnetic properties, was also calculated (3.4 mol% for BFT). Tests showed that the material is characterized by magnetic properties at low temperatures. At room temperature (RT), it has paramagnetic properties. It was also found that Gd3+ ions improve the magnetic properties of tested material.

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Direct current (DC) bias induced by the DC transmission and geomagnetically induced current is a critical factor in the abnormal operation of electrical equipment and is widely used in the field of power transmission and distribution system state evaluation. As the main affected component, the vector magnetization state of a transformer core under DC bias has rarely been studied, resulting in inaccurate transformer operation state estimations. In this paper, a dynamic vector hysteresis model that considers the impact of rotating and DC-biased fields is introduced into the numerical analysis to simulate the distribution of magnetic properties, iron loss and temperature of the transformer core model and a physical 110 kV single-phase autotransformer core. The maximum values of B, H and iron loss exist at the corners and T-joint of the core under rotating and DC-biased fields. The corresponding maximum value of the temperature increase is found in the main core limb area. The temperature rise of the 110 kV transformer core under various DC-biased conditions is measured and compared with the FEM (Finite Element Method) results of the proposed model and the model solely based on the magnetization curve B||H. The calculation error of the temperature rise obtained by the improved model is approximately 3.76-15.73% and is much less than the model solely based on magnetization curve B||H (approximately 50.71-66.92%).

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The oxidation of tetraselenatetracene (TSeT) by tetracyanoquinodimethane in the presence of dysprosium(III) tris(hexafluoroacetylacetonate), DyIII(hfac)3, produces black crystals of {TSeT1.5}●+[DyIII(hfac)4]- (1) salt, which combines conducting and magnetic sublattices. It contains one-dimensional stacks composed of partially oxidized TSeT molecules (formal averaged charge is +2/3). Dimers and monomers can be outlined within these stacks with charge and spin density redistribution. The spin triplet state of the dimers is populated above 128 K with an estimated singlet-triplet energy gap of 542 K, whereas spins localized on the monomers show paramagnetic behavior. A semiconducting behavior is observed for 1 with the activation energy of 91 meV (measured by the four-probe technique for an oriented single crystal). The DyIII ions coordinate four hfac- anions in [DyIII(hfac)4]-, providing D2d symmetry. Slow magnetic relaxation is observed for DyIII under an applied static magnetic field of 1000 Oe, and 1 is a single-ion magnet (SIM) with spin reversal barrier Ueff = 40.2 K and magnetic hysteresis at 2 K. Contributions from DyIII and TSeT●+ paramagnetic species are seen in EPR. The DyIII ion rarely manifests EPR signals, but such signal is observed in 1. It appears due to narrowing below 30 K and has g4 = 6.1871 and g5 = 2.1778 at 5.4 K.

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As technology advances, the demand for effective microwave-absorbing materials (MAM) to mitigate electromagnetic wave interference is growing. Two-dimensional (2D) materials are increasingly favored across various fields for their high specific surface area, electrical conductivity, low density, and dielectric loss properties. This study presents lightweight nanocomposites composed of graphene nanoplatelets blended with epoxy resin (ER) and cardanol with silane-functionalized (SFC) as a toughening agent. The resulting nanocomposites exhibit a high surface roughness of 130 nm and an enhanced hydrophobicity, as evidenced by a high contact angle. Notably, the ER/SFC/GNP sample at 3 wt% (0.075 g) achieves a minimum reflection loss value of -18 dB at a thickness of 10 mm, indicating improved impedance matching and enhanced dielectric loss capability. The increasing damping factor ratio to approximately 0.95 further augments the reflection loss performance. The research aims to develop cost-effective, efficient, lightweight graphene-based nanocomposite absorbers.