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Barium hexaferrite (BaFe12O19) and Ni–Zn ferrite (Ni0.6Zn0.4Fe2O4) powders were synthesized using the microwave hydrothermal method. Composite samples with varying ratios {x(Ni0.6Zn0.4Fe2O4) + (1 − x) (BaFe12O19)} (where x ranged from 0 to 1.0) were prepared through mechanical mixing. The pure and composite samples were subjected to a 4-h heat treatment at 800 °C. The structural characteristics of the pure samples were analyzed using X-ray diffraction (XRD), revealing the hexagonal structure of BaFe12O19 and the spinel structure of Ni0.6Zn0.4Fe2O4. Morphological properties were investigated using field emission scanning electron microscopy (FESEM). The results confirmed a hexagonal morphology for BaFe12O19, a spherical morphology for Ni0.6Zn0.4Fe2O4, and a mixed morphology for the composites, with grain sizes ranging from 50 to 200 nm. The optical properties were explored through UV–Vis absorption studies, and the optical energy gap values were determined using the Tauc plots. The magnetic behavior of the samples was studied by analyzing magnetic hysteresis loops. Pure samples exhibited a smooth hysteresis behavior, while composite samples displayed a step-like pattern. A possible relation between the magnetic interaction between the two different materials in the composites was investigated. [ABSTRACT FROM AUTHOR]

Based on magnetic fluids, new effective technical devices have been implemented, such as magnetic fluid bearings, seals, and dampers. The magnetic-viscous effect inherent to magnetic fluids can not only improve the properties of magnetic fluid units, but significantly complicate their operation after a long stop. This refers to the so-called «stop effect», which occurs due to an abnormally high limiting shear stress in a nanostructured liquid. The plastic properties of the magnetic fluid are experimentally studied depending on the following parameters: shear stress, temperature, structure formation time. The destruction of the nanostructure of the magnetic fluid begins after the shear stress exceeds a certain critical value. At stresses below the critical, but above the limiting shear stress, the displacement of the solid surface occurs by overcoming the boundary friction of the magnetic fluid on the solid surface. The experimentally established exponential course of the temperature dependence of the shear rate reflects the nature of the forces that determine the internal friction in the magnetic fluid.

The magnetic properties of core/shell nanoparticles (NPs) depend on the various parameters, including the magnetic interactions, but these effects have not been well studied. Here, we systematically investigated the structure and magnetic properties of Fe3O4@CoFe2O4 core/shell NPs. X-ray diffraction (XRD), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) confirmed the formation of Fe3O4@CoFe2O4 core/shell NPs. Magnetic measurements of the core/shell NPs were performed on both dried-pressed and well-dispersed in wax states. For the dried-pressed NPs, we found that the temperature-dependent magnetization curves of core/shell NPs vary significantly compared to that of core NPs due to spin interactions at the core/shell interface. Besides, the hysteresis loops of the core/shell NPs at 10 K are constricted, probably due to the interparticle interaction. For the core/shell NPs dispersed in wax, the hysteresis loops were smooth at all temperatures between 10 and 300 K due to the attenuated interparticle interaction. The high HC of 9.14 kOe (at 10 K) of the dispersed NPs is twice larger than that of the dried-pressed powders (4.23 kOe). Our study provides new insights into the effects of shell thickness and interparticle interaction on the magnetic properties of Fe3O4@CoFe2O4 core/shell NPs.

This research investigates the Models of eighth-grade students in Turkey pertaining to magnets and magnetic interactions, while also examining the consistency of these models within themselves. Additionally, a comparative assessment is conducted by comparing the current data with data collected from eighth-grade students a decade earlier. The study comprises 59 students in the first phase and 45 students in the second phase, all of whom briefly received formal instruction on magnetism during fourth grade. The focus of the analysis centers on identifying the students' Models and evaluating their coherence across diverse contexts in both phases. Surprisingly, despite the passage of ten years, the mental model patterns exhibited by the students in both studies remain remarkably similar. Three primary categories emerged from the students' Models of magnets, including attraction and repulsion, magnetic poles, and the composition and functionality of magnets. However, noticeable distinctions between the two studies are evident. In the earlier study, the students' responses to survey questions displayed a greater variety and detail in comparison to the responses from the later study. Moreover, the second study revealed fewer instances of inconsistent Models concerning the magnetic interaction between magnets and nails, but more instances of inaccurate Models compared to the first study. The findings of this investigation offer valuable insights to educators, guiding them in designing effective lessons and activities aimed at helping students overcome their inaccurate and inconsistent Models. [ABSTRACT FROM AUTHOR]

In this study, the effects of A-site La and Ca defects with Mn2+ doping on the structure, magnetic phase transition, magnetocaloric effect, critical indices, and magnetic interactions of La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres were investigated. The results indicated that the critical parameters of La 0·66 Ca 0·33 MnO 3 porous nanospheres were similar to those of the short-range ordered Ising model. The A-site La-defect Mn2+ doping makes the critical parameters β and γ tend to the Ising model and mean-field model, respectively. When A-site Ca-defect Mn2+ doping is obtained, β and γ tend to follow the Ising model and 3D-Heisenberg model, respectively. The phase transition exhibited a second-order ferromagnetic-paramagnetic transition for all samples. The A-site defect Mn2+ doping in La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres enhanced the Curie temperature to near room temperature without affecting magnetic entropy change. The effect of A-site defect Mn2+ doping on the magnetic interaction of La 0.66-x Ca 0.33-y Mn 1+x + y O 3 was visualized by the first-order reversal curve. The variation of interaction field distribution at the Curie temperature and 300 K indicated that exchange interaction was dominant at high temperature and dipole interaction was dominant at the Curie temperature. [Display omitted] • Non-stoichiometric La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres were prepared using a solvothermal method. • The role of Mn2+ doped in La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres were investigated. • The Mn2+ doping in La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres enhanced the T C to near RT without affecting | -ΔS M max |. • The changes in magnetic interaction of La 0.66-x Ca 0.33-y Mn 1+x + y O 3 porous nanospheres were visualized by FORC. [ABSTRACT FROM AUTHOR]

We have extended the Helfrich's spontaneous curvature model of the equilibrium vesicle by adding the interaction between magnetic field and the constituent molecules to supply an explaination in principle of the emerging manipulated deformation of a magnetic vesicles such as the reversibly deformation of artificial stomatocyte. The small deformation can be measured by birefringence. Here, we present the derivations of formulas in detailed to reveal the perturbation of deformation $\psi $ ψ under two cases. New features, for example, a 'phase transition' of shape will occur with increasing of $B$ B from $B_1^*$ B 1 ∗ to $B_2^*$ B 2 ∗ for ${\rm \Delta}\chi \lt 0$ Δ χ < 0 , in which the major axis of ellipse was rotated by 90°, have been revealed. It is worthy for experimenter to demonstrate the 'phase transition'. The significance of imaginary relation ($B_1^* \lt B\lt B_2^*$ B 1 ∗ < B < B 2 ∗ ) is also waiting to be uncovered. [ABSTRACT FROM AUTHOR]

Hierarchical microstructures and synergistic dielectric-magnetic effect are expected to satisfy the improvement of microwave absorption, but still face considerable challenges. Herein, we employ the electrospinning strategy and thermal reduction engineering to fabricate hierarchical carbon fibers with multi-dimensional magnetic configurations, in which Ni spheres are embedded in carbon fibers and Co sheets are anchored on the surface of carbon fibers. The results indicate that abundant hetero-interfaces combined with electromagnetic synergy promote impedance characteristics and strengthen interfacial polarization, magnetic domains with multi-dimensional configurations contribute to magnetic loss by means of intrinsic ferromagnetic resonance and magnetic coupling, and unique hierarchical architectures result in multiple scatterings. As a result, the minimum reflection loss (R L,min) achieves a high value of −45.9 dB at 4 mm and the effective absorption bandwidth (EAB) reaches 5.9 GHz at a thickness of 2.8 mm. It is believed that this design concept opens up a novel strategy in fabricating multi-dimensional magnetic configurations and the absorbers with high-efficient absorption performance exhibit promising the potential in managing electromagnetic radiation. [Display omitted] [ABSTRACT FROM AUTHOR]

Electromagnetic mini valves have attracted great interest in medical devices for their excellent performance and high integration. In state-of-the-art research, most mini valves have only two working states, while certain ones featuring three to four working states necessitate multiple driving sources. To solve these problems, a novel tristable electromagnetic mini valve with three stable working states achieved by a single coil was proposed. The actuation mechanism of this mini valve mainly comprises a cylindrical magnet (CM) and a ring magnet (RM) coaxially arranged. In the absence of current through the coil, the stability of the magnets is upheld by their mutual repulsion and the attraction of the iron core. Upon modifying both the magnitude and orientation of the current, one of the magnets traverses from one terminus to another each time. The two magnets are either stationary at the start point or the endpoint. Thereby, four position relationships are formed, three of which are stable. The minimum response time and energy consumption are 3.75 ms and 0.013 J, respectively. The working pressure of the valve ranges from 0 to 200 kPa. The maximum flow rate and back pressure reach 10.5 L/min and 180 kPa, respectively. A tristable design contributes to lower energy consumption, and the three-working-state function actuated by a single coil facilitates a diminution in the size of the mini valve. Consequently, a diminished quantity of valves is realized for multiple degree-of-freedom pneumatic actuator control, which promotes the miniaturization of the whole system. The dimensions and performance of the proposed mini valve substantiate its potential in pneumatic medical devices. [Display omitted] • The three-way electromagnetic mini valve achieves three stable working states through a single coil drive. • A tristable design is realized by the attraction of the iron core and the repulsion between two magnets. • The CM flips during the transformation, thus forming four states, three stable working states and a transition state. • The considerable magnet repulsion keeps the magnets stable, thereby increasing the working pressure and back pressure. [ABSTRACT FROM AUTHOR]

• FeCo alloy nanowires were successfully prepared into AAO templates by electrodeposition method. • The influence of diameter of FeCo alloy nanowires on magnetic properties was investigated by FORCs curves. • The interaction force between the FeCo alloy nanowires increased with the increasing diameter. • The domain state of FeCo alloy nanowires changed from SD to MD with the increasing diameter. FeCo alloy nanowires have potential applications in data storage, magnetic sensors and spintronic devices. In this paper, FeCo alloy nanowires with varying diameters were fabricated within an anodic aluminum oxide (AAO) template using electrodeposition method at a constant potential. Characterization of the morphology and structure revealed that the polycrystalline body-center-cubic(bcc) FeCo alloy nanowires were obtained. The influence of diameter of FeCo alloy nanowires on magnetic interaction, domain state and magnetic mechanism was investigated through a first-order reversal curve (FORC) analysis. The findings showed that with an increase in the diameter of FeCo alloy nanowires from 20 nm to 60 nm and 100 nm, the interaction force between the FeCo alloy nanowires increased, the domain state of FeCo alloy nanowires changed from Single Domain (SD) to Multi-Domain (MD), the magnetic reversal mode changed from coherent reversal mode to curling reversal mode. [ABSTRACT FROM AUTHOR]

• A double-shell 3 d -Gd cluster, {Gd 22 Ni 22 }, was elaborately constructed by solvothermal conditions. • {Gd 22 Ni 22 } cluster exhibits a large magnetocaloric effect (46.0 J kg−1 K−1 at 2.0 K for ΔH = 7 T), which is one of the largest among all the high-nuclearity Ni–Gd clusters. • The large magnetic entropy change of {Gd 22 Ni 22 } cluster is closely related to its weak magnetic interaction. Atomically well-defined metal nanoscale clusters have attracted significant interest owing to their fascinating structures and wide potential applications. The Gd (III) containing clusters, in particular, attract great research attention due to their potential magnetic refrigeration applications. Here, we report the synthesis of a gigantic double-shell 3 d -Gd cluster, {Gd 22 Ni 22 }, which is composed of [Gd 5 Ni 2 (μ 2 -OH) 4 (μ 2 -OH) 6 ]9+ and [Gd 6 Ni 9 (μ 2 -OH) 20 (μ 3 -OH) 10 ]6+ structural units. Magnetic characterization reveals that the {Gd 22 Ni 22 } cluster exhibits a large magnetocaloric effect (MCE), with an isothermal magnetic entropy change of 46.0 J kg−1 K−1 at 2.0 K for ΔH = 7 T, which is one of the largest among all the high-nuclearity Ni–Gd clusters. The large magnetic entropy change of {Gd 22 Ni 22 } cluster is closely related to its weak magnetic interaction. [ABSTRACT FROM AUTHOR]

• Different electronic and steric effects of amine backbone led to linear-type M-Dy-M, one-dimensional (1D) chain and interlayer-type structures of complexes. • Align the magnetic easy axis of lanthanide ions as closely as possible with the direction of M-M facilitating the mitigation of quantum tunneling of magnetization. • Notable hysteresis loops at maximum temperature of 3.5 K, 7.5 K, and 4 K are observed for Cu 2 Dy, Zn 2 Dy and Ni 2 Dy complexes, respectively. Series of 3d-4f heterotrinuclear complexes [ M Dy M ] (M =Zn, Cu, Ni) with formula [Cu 2 (L1) 2 DyCl 2 (H 2 O)]·Cl·MeCN (1), [Cu 2 (L2) 2 DyCl 2 ] n (2), [Cu 2 (L3) 2 DyCl 2 (MeOH) 2 ]·Cl·(MeOH) 3 (3), [Zn 2 (L1) 2 DyCl 2 (H 2 O)]·Cl·MeCN (4) and [Ni 2 (L1) 2 DyCl 3 ]·(CH 2 Cl 2) 2 (5) were constructed by three hexadentate compartment Schiff bases (L1 = N ,N'-bis(3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine; L2 = N ,N'-bis(3-methoxysalicylidene)-1,3-propanediamine; L3 = N ,N'-bis(2‑hydroxy-3-methoxybenzylidene)-1,2-phenylenediamine). Different electronic and steric effects of amine backbone lead to linear-type M -Dy- M , one-dimensional (1D) chain and interlayer-type structures of complexes 1 – 5 , respectively. Among these, complexes 1, 4 and 5 were constructed as the M -Dy- M linear-type coordination configuration containing diamagnetic zinc(II) ions and paramagnetic copper(II) ions or nickel(II) ions respectively. Molecular magnetic studies reveal that complexes 1, 4, 5 and chain complex 2 exhibited significant single-molecule magnets (SMMs) behavior and the notable hysteresis loops at maximum temperature of 3.5 K, 3 K, 7.5 K, and 4 K are observed, which are comparable among the outstanding heteronuclear (d/f) SMMs constructed by Schiff base ligands. Series of 3d-4f heterotrinuclear [MDyM] SMMs were constructed, different electronic and steric effects of amine backbone lead to very different structure and displaying significant magnetic relaxation with hysteresis loops at maximum temperature of 3.5 K, 3 K, 7.5 K, and 4 K, respectively, which are comparable among the outstanding heteronuclear (d/f) SMMs constructed by Schiff base ligands. [Display omitted] [ABSTRACT FROM AUTHOR]

Melilite structural materials have been widely studied in the past two decades due to their interesting physical properties, such as noncollinear magnetism and multiferroicity. Here, we present a theoretical investigation on the electronic and magnetic properties of melilite structural materials Ba 2 FeSi 2 O 7 and Ba 2 CoGe 2 O 7. First-principles calculations confirm that Ba 2 FeSi 2 O 7 and Ba 2 CoGe 2 O 7 are both antiferromagnetic semiconductors with the magnetic easy axis being along the [110] direction. Two flat bands with a bandwidth of less than 20 meV, which come from the d 3 z 2 − r 2 orbitals of Fe2+ or Co2+ ions, are found in both materials. More interestingly, we find that the magnetocrystalline anisotropy energy of the Ba 2 FeSi 2 O 7 is about 5.19 meV per unit cell, which is more than eight times larger than that of Ba 2 CoGe 2 O 7. Further calculations show that their MAEs are mainly contributed by the single-ion anisotropy. The perturbation calculations indicate that the different electron numbers in the d orbitals and their different orbital occupations in the two materials lead to the large difference in their single-ion anisotropy. Our work could be helpful to understand the magnetic behaviors in similar melilite structural materials. • The magnetic properties of Ba 2 FeSi 2 O 7 and Ba 2 CoGe 2 O 7 are studied by the DFT calculations. • Two flat bands with a bandwidth of less than 20 meV are found in Ba 2 FeSi 2 O 7 and Ba 2 CoGe 2 O 7. • Ba 2 FeSi 2 O 7 has a large MAE of 5.19 meV per unit cell, which is more than eight times larger than that of Ba 2 CoGe 2 O 7. • The different orbital occupations lead to the large differences in their single-ion anisotropy. [ABSTRACT FROM AUTHOR]

In this paper, the magnetocaloric properties, phase transitions, and critical properties of Mn 5 Ge 3-x V x (x = 0.1, 0.2, and 0.3) compounds prepared by arc melting were investigated. The incorporation of V in Mn 5 Ge 3-x V x alloys leads to a reduction in both the Curie temperature and the magnetic entropy change. Analysis of the isothermal magnetization curves using common methods such as Arrott curves, normalized curves, and Landau theory reveals that the system undergoes a second-order phase transition. Furthermore, the temperature-averaged entropy change (TEC) at 1–7T fields and the field hysteresis loss (HL) at 7T were calculate. The study then employs a modified Arrott diagram, the Kouvel-Fisher method, and critical isotherm curves to examine the critical behavior in the vicinity of the phase transition. Additionally, the accuracy of these critical exponents using Widom's scaling laws and scaling equations were validated. Further analysis results indicate that the spin coupling in the phase transition of Mn 5 Ge 3-x V x exhibits 3D Ising behavior, characterized by magnetic exchange decay rates of J (r) ≈ r −4.83, r −4.75, and r −4.77. These spin interactions are of the short-range extension type beyond the nearest neighbors, and the spin interactions extend beyond the nearest neighbors, potentially related to the Mn–Mn interactions with varying exchange strength magnitudes. • The magnetic transition is confirmed by different techniques. • Determine the hysteresis loss in the closed region between M(H) at 7T. • The.|ΔSM|, TEC, RCP, and RC of the Mn5Ge3-xVx system were investigated. • By analyzing the critical behavior, the critical index values are closer to the 3D Ising generic class. • The eigenvalues of the magnetic interaction are J(r) ≈ r − 4.83 、 r − 4.75 and r − 4.77 . [ABSTRACT FROM AUTHOR]

Composites of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) have been prepared by the high-energy planetary ball mill method. The magnetic composites are characterized by employing X-ray Diffraction and High-Resolution Transmission Electron Microscopy (HRTEM) techniques. The percentage of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) in the composite has been obtained from the Rietveld analysis of XRD patterns. The average crystallite sizes of BHF and NZFO are found to be comparable in the composites. The magnetic properties of (1-x) BHF-(x) NZFO with x = 0 to 1 have been studied by measuring the magnetic hysteresis loop (M-H loop) for all the samples. The M-H loops are analyzed by plotting the loop width (ΔH) versus magnetization (M). The magnetic hysteresis loops for the BHF and NZFO are found to be symmetric in all the quadrants. However, symmetry breaks in M-H loops for composites. The symmetry breaking in magnetic hysteresis loops of the bi-magnetic composite suggests a new approach to analyzing the magnetic interaction between magnetic phases in the magnetic composites. [ABSTRACT FROM AUTHOR]

Hierarchical engineering of suitable dielectric‐magnetic multicomponents shows good performance for microwave absorbers, but still face bottlenecks. Herein, hierarchical double‐shelled nanotubes (DSNTs), in which the inner magnetic tubular subunits are assembled by magnetic‐heteroatomic components through cation‐exchange reactions, and the outer dielectric MnO2 nanosheets strengthen the synergistic interactions between confined heterogeneous interfaces are ingeniously designed and constructed. Hetero‐interfaces induced polarization is proposed to investigate the interfacial relaxation mechanism, and magnetic loss, closely related to the micrometer‐scale magnetic units, is mainly clarified by the magnetic interaction composed of magnetic coupling and magnetic diffraction; both of them are clearly confirmed by Lorentz off‐axis electron holography. The obtained hierarchical DSNTs demonstrate efficient microwave absorption with an optimal reflection loss of −54.7 dB and qualified absorption bandwidth of 9.5 GHz owing to desirable heterogeneous interfaces, multiple magnetic heteroatomic components and hollow hierarchical microstructures. This strategy inspires a generalized methodology for the engineering of hollow hierarchical configurations with multishells, the combination of proposed hetero‐interfaces induced polarization and microscale magnetic interaction broadens the dielectric‐magnetic synergistic mechanism of the topography–performance relationship for microwave absorption materials. [ABSTRACT FROM AUTHOR]

In this work, we report a self-assembly method to fabricate a single layer of Co nanorods to study their magnetostatic interaction behavior. The Co nanorods with cambered and flat tips were synthesized by using a solvothermal route and an alcohol–thermal method, respectively. Both of them represent hard magnetic features. Co nanorods with cambered tips have an average diameter of 10 nm and length of 100 nm with coercivity of 6.4 kOe, and flat-tip nanorods with a 30 nm diameter and 100 nm length exhibit a coercivity of 4.9 kOe. They are further assembled on the surface of water in assistance of surfactants. The results demonstrate that the assembly type is dependent on the magnetic induction lines direction. For Co nanorods with flat tips, most of magnetic induction lines are parallel to the length direction, leading to an assembly that is tip to tip. For Co nanorods with cambered tips, they are prone to holding together side by side for their random magnetic induction lines. Under an applied field, the Co nanorods with flat tips can be further aligned into a single layer of Co nanorods. Our work gives a possible mechanism for the magnetic interaction of Co nanorods and provides a method to study their magnetic behavior. [ABSTRACT FROM AUTHOR]

Improving the thermoelectric (TE) performance of Bi2Te3‐based flexible films remains a huge challenge. Herein, high‐performance Ni/epoxy/Bi0.5Sb1.5Te3 magnetic flexible TE films are prepared by incorporating Ni nanoparticles (Ni‐NPs). Atomic‐resolution STEM investigation demonstrates that Te vacancies induced by the orientation reaction between Ni‐NPs and Te from Bi0.5Sb1.5Te3 trigger the presence of negatively charged V‴Bi(V‴Sb) and Bi′Te(Sb′Te) anti‐site defects and atomic‐sized electric field in the magnetic flexible TE films and further cause the acceleration movement and hopping migration of carriers. The transport measurements indicate an increased carrier concentration due to the anti‐site defects, while the significant increase of carrier mobility originates from the acceleration movement of carriers. The magnetic scattering and hopping migration of carriers are responsible for maintaining large Seebeck coefficient. As compared to epoxy/Bi0.5Sb1.5Te3 flexible TE film, the maximum power factor of the magnetic flexible TE film with 0.1% Ni‐NPs reaches 2.74 mW m−1 K−2 at 300 K and increases by 61%, while the cooling temperature difference increases by 250%. [ABSTRACT FROM AUTHOR]

Solid-solid phase transformations can affect energy transduction and change material properties (e.g., superelasticity in shape memory alloys and soft elasticity in liquid crystal elastomers). Traditionally, phase-transforming materials are based on atomic- or molecular-level thermodynamic and kinetic mechanisms. Here, we develop elasto-magnetic metamaterials that display phase transformation behaviors due to nonlinear interactions between internal elastic structures and embedded, macroscale magnetic domains. These phase transitions, similar to those in shape memory alloys and liquid crystal elastomers, have beneficial changes in strain state and mechanical properties that can drive actuations and manage overall energy transduction. The constitutive response of the elasto-magnetic metamaterial changes as the phase transitions occur, resulting in a nonmonotonic stress-strain relation that can be harnessed to enhance or mitigate energy storage and release under high-strain-rate events, such as impulsive recoil and impact. Using a Landau free energy-based predictive model, we develop a quantitative phase map that relates the geometry and magnetic interactions to the phase transformation. Our work demonstrates how controllable phase transitions in metamaterials offer performance capabilities in energy management and programmable material properties for high-rate applications. [ABSTRACT FROM AUTHOR]

Spin reorientation transition is an ubiquitous phenomenon observed in magnetic rare earth orthferrites RFeO 3 , which has garnered significant attention in recent years due to its potential applications in spintronics or magnetoelectric devices. Although a plenty of experimental works suggest that the magnetic interaction between R 3+ and Fe 3+ spins is at the heart of the spin reorientation, but a direct and conclusive theoretical support has been lacking thus far, primarily due to the challenging nature of handling R 4 f electrons. In this paper, we explored DyFeO 3 as an example by means of comprehensive first principles calculations, and compared two different approaches, where the Dy 4 f electrons were treated separately as core or valence states, aiming to elucidate the role of Dy 4 f electrons, particularly in the context of the spin reorientation transition. The comparison provides a solid piece of evidence for the experimental argument that the Dy 3+ -Fe 3+ magnetic interactions play a vital role in triggering spin reorientation of Fe 3+ moments at low temperatures. The findings revealed here not only extend our understanding on the underlying mechanism for spin reorientation transition in RFeO 3 , but also highlight the importance of explicit description of R 4 f electrons in rationally reproducing their structural, electronic and magnetic properties., (© 2024 IOP Publishing Ltd.)

The current work reports an unprecedented multifunctional material with optical activity and a modified magnetic response by a unique combination of doping with P and Fe into the spinel LiMn 2 O 4. Through inductively coupled plasma – optical emission spectroscopy, X-ray absorption near-edge spectroscopy, X-ray diffraction and scanning transmission electron microscopy, the chemical composition, oxidation state and the crystalline structure are determined. Solid-state UV-Vis spectroscopy, magnetic susceptibility and electronic conductivity reveal the critical importance of the interaction between iron and phosphorus when simultaneously doping the crystalline structure of LiMn 2 O 4. The presence of Fe and P considerably increases charge carrier concentration as a mechanism for enhancing electronic conductivity. Fe and P doping also creates Fe-Fe spin interactions that allow double electron optical excitations. This opens a pathway to create multifunctional materials for light-assisted charging lithium-ion batteries. P doping also induces the formation of magnetic clusters arising from the Fe-O-Fe, Fe-O-Mn and Mn-O-Mn spin exchange interactions. The magnetic response of the materials is strongly influenced by the relative amount of Fe in octahedral or tetrahedral sites of the spinel structure. Such ferrimagnetic behaviour has not been reported before LiMn 2 O 4 doped with Fe or P separately. The potential applicability of this newly identified magnetic feature was demonstrated by a significant capacity gain when a lithium-ion cell is exposed to a static external magnetic field. • Simultaneous P and Fe doping of the LiMn 2 O 4 spinel develops new ferro/ferrimagnetic properties in this material. • Phosphorous stabilizes iron-iron magnetic interactions, unseen in previous Fe doped LiMn 2 O 4. • Iron-iron magnetic interaction gives rise to double optical electron excitation and ferro/ferrimagnetic features. • Under magnetic field, ferromagnetic P and Fe doped LiMn 2 O 4 delivers higher capacity gains than other generic LIB materials. • Enhanced capacity gains occur due to an increased magnetohydrodynamic effect on the surface of the particles. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of double perovskites Sr2BWO6 (B = Co, Ni, Cu) were studied for each of three magnetic configurations nonmagnetic, ferromagnetic, and antiferromagnetic by using density functional theory in generalized gradient approximations (GGA) and strong correlation correction (GGA + U). Due to magnetic transition from antiferromagnetic to nonmagnetic phase, an electron transition occurred from semiconductor to metal in the tetragonal structure of Sr2CoWO6, and from insulator to metal in the two tetragonal structures of Sr2NiWO6 and Sr2CuWO6. Furthermore, in Sr2CoWO6, another electron transition occurred from metal to half-metal, due to the octahedral rotation of cobalt and possibly because of changes in the magnetic interactions resulting from it. Structurally, the lattice parameters of Sr2CoWO6 and Sr2NiWO6 were decreased by eliminating magnetic interactions. But, the lattice parameters of Sr2CuWO6 was increased with loss of magnetic order, due to the dominance of Jahn-Teller deviation.

In this work, we report a self-assembly method to fabricate a single layer of Co nanorods to study their magnetostatic interaction behavior. The Co nanorods with cambered and flat tips were synthesized by using a solvothermal route and an alcohol–thermal method, respectively. Both of them represent hard magnetic features. Co nanorods with cambered tips have an average diameter of 10 nm and length of 100 nm with coercivity of 6.4 kOe, and flat-tip nanorods with a 30 nm diameter and 100 nm length exhibit a coercivity of 4.9 kOe. They are further assembled on the surface of water in assistance of surfactants. The results demonstrate that the assembly type is dependent on the magnetic induction lines direction. For Co nanorods with flat tips, most of magnetic induction lines are parallel to the length direction, leading to an assembly that is tip to tip. For Co nanorods with cambered tips, they are prone to holding together side by side for their random magnetic induction lines. Under an applied field, the Co nanorods with flat tips can be further aligned into a single layer of Co nanorods. Our work gives a possible mechanism for the magnetic interaction of Co nanorods and provides a method to study their magnetic behavior.

Five new polybromide compounds containing tris-chelates of 1,10-phenanthroline and 2, 2-bipyridine as counter cations are described: [Mn(phen)3](Br3)2 (1), [Co(phen)3](Br3)3 (3) and [M- (phen)3](Br3)(Br8)1 =2 where, M=Fe (2), Cu(4) or Zn(5). All are obtained by self assembly in solution starting from divalent transition metal bromides and bromine along with the ligand. In the case of CoBr2, bromine acts as a tribromide precursor as well as oxidising agent. The Mn compound is isomorphous with the corresponding triodide and analogously contains one short and one normal trihalide ion. The Co compound contains one bent but symmetric Br3 ion. The three compounds containing the Z-shaped octabromide ion are isostructural. While the cation in 1 has a crystallographically imposed C3 symmetry, the tris chelates in the other four compounds have near trigonal symmetry. Unusually, the trigonally compressed octahedral cation in 4 has six almost equal Cu N bond distances. Attempts to prepare bpy analogs of 1 resulted in a new dibromo-bridged compound [Mn2Br2(bpy)4](Br3)2 (6) and a dioxo-bridged compound [Mn2O2(bpy)4](Br3)3 (7). The mixed valence cation in 7 formed by bromine oxidation of MnBr2, followed by disproportionation, is well known with other anions. All the paramagnetic compounds (1, 4, 6, 7) give resolved EPR spectra since the bulky anions help to magnetically isolate the cations. The unsymmetric dibromo bridges in 6 produce a net, albeit weak, ferromagnetic coupling between the two [Mn(bpy)2] ²+ fragments. Raman as well as electronic spectra are reported for all compounds. Raman bands, though significantly different even for isostructural compounds, may be understood in terms of Br3 ions and Br2 molecules. All compounds give luminescence from phen and bpy both in solid and solution states, modulated by the coordinated metal io [ABSTRACT FROM AUTHOR]

A magnetic-geared motor (MGM) has attractive features including high torque density, which contributes to reducing the overall size and weight in comparison with conventional motors, especially for low-speed and high-torque applications. The MGM consists of a magnetic gear (MG) and a permanent magnet (PM) motor, and they share one high-speed rotor (HSR). In general, the HSR has a structure of surface PM (SPM) in order to magnetically decouple between the MG and the PM motor by the HSR yoke. However, this structure is the cause of the worse eddy current loss in the HSR magnets. In a previous study, to resolve the issue, a structure of interior PM (IPM) that the HSR magnets are embedded in the HSR yoke was proposed. It was clear that the eddy current loss in the magnets can be reduced and the efficiency is improved. In the IPM structure, however, there is concern that the MG and the PM motor have magnetically interacted and its influence has not been clarified. This article presents the investigation of the magnetic interaction of the IPM-type MGM by using the finite-element method (FEM). The influence of the interaction is described by comparing SPM and IPM types. Moreover, the magnetic interaction is demonstrated by a prototype IPM-type MGM. [ABSTRACT FROM AUTHOR]

Regulated magnetic interactions in semiconductor nanometer structure have a strong application background in spin electronics and quantum information processing. This paper mainly studies the influence of electron interaction on the magnetic coupling between diluted magnetic semiconductor quantum dots embedded in semiconductors. Taking into account the interaction between electrons, we will calculate the RKKY Magnetic interaction between the local spins of two diluted magnetic semiconductor quantum dots embedded in the semiconductor applying the Keldysh Green's function method. For the electronic interaction, we use the simple self-consistent mean-field approximation. [ABSTRACT FROM AUTHOR]

In this article, we studied a magnetic levitation system which was composed of a high-temperature superconducting (HTS) coil, HTS bulks, and a ferromagnetic material (rail). We set two magnetic levitation systems in one ferromagnetic rail. We analyzed the levitation force depending on changing the distance between HTS coils of each direction of current flowing. As a result of comparing two poles that has current flowing through its coils in one direction and two poles that has current flowing through its coils in different directions, the model which had the coils in one direction was better. A reason for this result is discussed comparing with the magnetic flux density and the stress tensor in a ferromagnetic rail. In addition, the distance between coils was also important for the magnetic interaction. We show the tendency of levitation force obtained by changing the distance between coils in each direction of current flowing and explain the reason. In this article, it is found that a greater force can be obtained by using magnetic field interaction effectively. We optimized arrangement and magnetic pole combination and we succeeded to improve the levitation property. [ABSTRACT FROM AUTHOR]

Piezoelectric stack transducers in d33 mode have a much higher mechanical-to-electric energy conversion efficiency compared with d31 mode piezoelectric harvesters. However, multilayered piezoelectric stacks usually operate in off-resonance due to the higher stiffness and thereby have a lower power output under low-frequency excitations. This paper proposes to apply the dynamic magnetic pre-loading to a piezoelectric stack transducer to significantly increase the power output. The energy harvesting system consists of a multilayered piezoelectric stack with a compliant force amplification frame, a proof mass, and two magnets configured in attraction. The static force–displacement relationship of the magnets is identified from experiments and extended to a dynamic model capable of characterizing the dynamic magnetic interaction. An electromechanical model is developed based on the theoretical derivation and the experimentally identified parameters to predict the voltage outputs under different resistive loads. Approximate analytical solutions are derived by using the harmonic balance method and show good agreements with the numerical and experimental results. The performance of the system is examined and compared with that of the harvester without magnetic pre-loading. The influences of the distance between the two magnets and the electrical resistive loads on the power output are investigated. Results indicate the energy harvesting system with magnetic pre-loading can produce over thousand times more power than the system without magnetic pre-loading at the base excitation of 3 Hz and 0.5 m/s2, far below the resonance at 243 Hz [ABSTRACT FROM AUTHOR]

A series of highly ordered multilayer [FeCoCu/Cu(x)]30 ($0 \le x \le 40$ nm with FeCoCu layer thickness fixed 1000 ± 100 nm) nanowire arrays in alumina membrane (200 nm diameter) was fabricated by electrodeposition from a single electrolytic bath. The body-centered cubic (bcc) phase of FeCoCu-alloy separated by a well-defined face-centered cubic (fcc) phase of Cu spacer is confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. The objective of the present investigation is to tune the magnetic properties through inter- and intra-wire interactions between the FeCoCu layers separated by non-magnetic Cu(x) layers in the multilayer nanowire array. Ferromagnetic resonance (FMR) study was performed in a flip-chip geometry to explore the magnetization dynamics. FMR measurements confirm the decrease of resonance field ($H_{r}$), whereas resonance linewidth ($\Delta H$) and FMR absorption increase with the increase in the Cu layer thickness. It may be argued that through inter-/intra-nanowires interactions, the Landau–Lifshitz–Gilbert damping provides the most physically sensible magnetization relaxation in multi-layered nanowires system. The values of the Gilbert damping parameters (intrinsic and extrinsic), obtained from the FMR linewidth analysis, exhibit a decrease from FeCoCu nanowire to [FeCoCu/Cu(5 nm)] nanowire. With further increase in the Cu thickness, both these parameters were observed to have increased. [ABSTRACT FROM AUTHOR]

In this study, the consequences of R3+ cationic radii on the dielectric, conductivity and magnetic response of selected RCrO3 perovskites are presented. The frequency-dependent real part of dielectric constant (ε′) and loss tangent (tan δ) were studied at 300 K and observed that at low frequency the values are high. From the conductivity (σAC) studies, we found that values of frequency exponent (s) are in the range 0.21–0.51 for the measured frequency range, which clearly indicates that the conduction mechanism is due to small polaron hopping. The magnetic studies reveal that all the synthesized samples exhibit magnetic phase transition (paramagnetic to antiferromagnetic) below the critical Neel temperature (TN) which is associated to Cr3+–O2−–Cr3+ exchange interaction and the value of TN decreases uniformly with decreasing R3+ cationic radii. Some samples show interesting magnetic behavior, along with isothermal hysteresis curve proposing the spin reorientation phase transition of Cr3+ magnetic ordering. [ABSTRACT FROM AUTHOR]

In this study, we examined the magnetic and electric properties of the Cu-doped Bi2-xCuxIr2O7 (x = 0,0.2,0.4,0.6). The X-ray diffraction confirmed that the Bi2-xCuxIr2O7 had a cubic structure. The electric transport properties indicate that the samples were in a metallic state when x < 0.4, and the metal-insulator transition occurred in the sample at x = 0.6. The behaviour of the resistivity in the composite material was produced by the electron-electron scattering process. The grain boundary effect played a dominant role in the conduction process. It was also found that the antiferromagnetic interactions enhanced with increasing Cu doping at first, but they weakened with further increases in Cu doping. These findings are explained based on the competition among the ferromagnetic Cu–Cu, antiferromagnetic Ir–Ir and antiferromagnetic Ir–Cu interactions. [ABSTRACT FROM AUTHOR]

In this study, we examined the magnetic and electric properties of the Cu-doped Bi2-xCuxIr2O7 (x = 0,0.2,0.4,0.6). The X-ray diffraction confirmed that the Bi2-xCuxIr2O7 had a cubic structure. The electric transport properties indicate that the samples were in a metallic state when x < 0.4, and the metal-insulator transition occurred in the sample at x = 0.6. The behaviour of the resistivity in the composite material was produced by the electron-electron scattering process. The grain boundary effect played a dominant role in the conduction process. It was also found that the antiferromagnetic interactions enhanced with increasing Cu doping at first, but they weakened with further increases in Cu doping. These findings are explained based on the competition among the ferromagnetic Cu–Cu, antiferromagnetic Ir–Ir and antiferromagnetic Ir–Cu interactions. [ABSTRACT FROM AUTHOR]

In this study, magnetic interaction is applied to a continuous structure as local negative-stiffness components to improve the vibration isolation performances and to extend the vibration isolation band. According to the theory of electromagnetic fields, the mechanical model of interaction force is established. This model is used to discover that the magnetic interaction can induce the negative stiffness property locally using appropriate structural parameters. Because different structural parameters of the magnets can increase the negative stiffness strength with different effects, the parameters of the continuous beam and magnets are adjusted for the design of accurate zero stiffness property locally. Then, the relationship between structural parameters and effective isolation bandwidth is established by deriving the solution of steady state around zero equilibrium. As the nonlinearity and zero-stiffness property only occur locally around zero equilibrium and the system displays the positive-stiffness property for large vibration amplitudes, the effective isolation band is significantly extended, and the amplitude–frequency curve is similar to the linear system at resonance. The relevant experiments demonstrate the remarkable tuning characteristic of structural parameters of magnets on the isolation features, which realize the improvement of isolation/protection effectiveness for time-lasting excitation at a low frequency. This study not only demonstrates the advantages of nonlinearity induced by local magnetic interaction on the improvement of isolation performances but also realizes a continuous structure with local quasi-zero stiffness applied in fields of low-frequency engineering structures. • Realizing adjustable negative stiffness by magnetic interaction. • Utilizing local property of magnetic force to realize quasi-zero-stiffness property. • Building the relation between structural parameters and effective isolation band. • Assembling the relevant experiment of continuous structure under magnetic field. [ABSTRACT FROM AUTHOR]