Search

Superconducting stiffness $\rho_s$ and coherence length $\xi$ are usually determined by measuring the penetration depth $\lambda$ of a magnetic field and the upper critical field $H_{c2}$ of a superconductor (SC), respectively. However, in magnetic SC, e.g. some of the iron-based, this could lead to erroneous results since the internal field could be very different from the applied one. To overcome this problem in Fe$_{1+y}$Se$_x$Te$_{1-x}$ with $x \sim 0.5$ and $y \sim 0$ (FST), we measure both quantities with the Stiffnessometer technique. In this technique, one applies a rotor-free vector potential $\textbf{A}$ to a superconducting ring and measures the current density $\textbf{j}$ via the ring's magnetic moment $\textbf{m}$. $\rho_s$ and $\xi$ are determined from London's equation $\textbf{j}=-\rho_s\textbf{A}$ and its range of validity. This method is particularly accurate at temperatures close to the critical temperature $T_c$. We find weaker $\rho_s$ and longer $\xi$ than existing literature reports, and critical exponents which agree better with expectations based on the Ginzburg-Landau theory., Comment: 10 pages, 10 figures

Magnetism has revolutionized important technologies, and continues to bring forth new phenomena in emergent materials and reduced dimensions. Here, using first-principles calculations, we demonstrate that the already-synthesized two-dimensional (2D) Ni-tetracyanoquinodimethane (Ni2(TCNQ)2) lattice is a stable ferromagnetism material with multiple spin-polarized Dirac cones. The conical bands in proximity of the Fermi level can be tuned by external tensile strain and show the fourfold degenerate electronic states at the critical tensile strain of ∼2.35%, whose energy dispersion is consistent with 2D Cairo pentagonal lattice. In addition, spin-orbital coupling can open a band gap at the Dirac point of A, leading to topologically nontrivial electronic states characterized by the non-zero Chern number and the edge states of nanoribbon. Our results offer versatile platforms for the realization of massless spintronics with full-spin polarization in 2D Cairo pentagonal Ni2(TCNQ)2 Lattice.

BaTiO3 ceramics doped with double perovskite Sr2KMoO6 (BT-SKM) are fabricated via solid-state reaction technology. The effects of SKM dopants on the structure, band gap and electrical/magnetic properties of BT are systematically studied. XRD and Raman spectra analysis show polycrystalline perovskite structure of the samples, which confirms the structural changes. With the addition of SKM dopants, the grain size of the samples decreases significantly. The band gaps of doped BT samples reduce, and the minimum band gap of BT-SCM is 1.77 eV, which is apparently reduced compared with the band gap of pure BT of 3.22 eV. However, the ferroelectric properties are weakened in samples doped with SKM. This ascribes to the introduction of more oxygen vacancies by dopants, which impedes the switching of domains, resulting in deterioration of ferroelectric properties. Furthermore, ferromagnetism of BT-SNM is observed, which may be attributed to the long-range exchange interaction between Ni2+ ions and oxygen vacancies. These results reveal the potential applications of these perovskite oxides in photovoltaic and memory devices.

In this study, the structural, morphological, and magnetic properties of hydrothermally synthesized Co0.5Ni0.5BixFe2-xO4 (x=0.00–0.10) nanosized spinel ferrites, (CoNiBiFO (x=0.00–0.10) NSFs), were investigated. The formation of CoNiBiFO NSFs phase was confirmed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the morphology of the NSFs. Magnetization revealed that undoped Co0.5Ni0.5Fe2O4 and Co0.5Ni0.5BixFe2-xO4 NSFs (except with x = 0.04) exhibit ferrimagnetic magnetism at 300 K. Only the hysteresis loops recorded from Co0.5Ni0.5Bi0.04Fe1.96O4 NSFs have superparamagnetic characteristics. Mixed Co0.5Ni0.5Fe2O4 NSFs have maximum remnant magnetization (Mr) of 23.5 emu/g, maximum saturation magnetization (MS) of 63.38 emu/g, and maximum magneton number (nB) 2.66 μB. However, Co0.5Ni0.5Bi0.04Fe1.96O4 NSFs have minimum MS of 28.25 emu/g and minimum nB as 1.22 μB among Bi3+ doped and undoped samples. The coercivity (HC) of undoped Co0.5Ni0.5Fe2O4 NSFs is 656 Oe. However, the Bi3+ ion-doped samples have a wide range of HC values between 101 Oe and 1038 Oe. The squareness ratios are in the range of 0.092–0.418 and multi-domain structure is assigned for all types of samples. The measured positive exchange bias (HE) magnitudes are 268 Oe and 290 Oe, respectively. Hysteresis loops recorded at 10 K proved that the products are ferrimagnetic. These coercivities showed that all the samples are magnetically harder at low temperatures. Positive HE values of 165 Oe and 297 Oe were measured from the nanoparticles (NPs) with x = 0.08 and x = 0.10 at 10 K. The SQR of the Co0.5Ni0.5Bi0.04Fe1.96O4 sample at 10 K is almost equal to the critical value of 0.5, and a single domain structure with uniaxial symmetry can be attributed for this sample. The other samples have SQRs in the range of 0.632–0.782 and multi-domain wall structure is assigned for them at 10 K.

Over the past four years, the magnetism of 2D magnets has been extensively studied by the full arsenal of probing techniques. 2D magnets can be incorporated to form heterostructures with clean and sharp interfaces, which gives rise to exotic phenomena as a result of the interfacial proximity effect. Here we report a detailed study of the spin (ms) and orbital (ml) moments of an epitaxial (CrSb/Fe3GeTe2)6 superlattice. The synchrotron-radiation based x-ray magnetic circular dichroism (XMCD) technique was performed to probe the microscopic magnetic properties of the superlattices in an elemental resolved manner. We unambiguously obtained a bulk-like moment of Fe3GeTe2 i.e., ms = 1.58 ± 0.2 μB/Fe and ml = 0.22 ± 0.02 μB/Fe. Future works to explore the tuning of the spin polarized band structure of 2D ferromagnetic superlattices will be of great interest and can have strong implications for both fundamental physics and the emerging spintronics technology.

A method of preparing passive materials suitable for magnetooptic interactions is shown using manganese implantation into gallium nitride (GaN) epitaxial layers, which establishes both dilute ferromagnetism and a three-level optical system with persistence to over 300 K. A sweep of thermal anneal parameters for a high implant dose into Mg-doped p-type GaN films is presented, and the materials are tested for both their magnetization and photoluminescence (PL). The optimal anneal process at 825 °C for 5 min maintains ferromagnetism with $T_{C}$ > 305 K, confirming magnetic alignment at room temperature with a coercivity of ~100 Oe. PL and spectrophotometry of the optimally prepared materials show the effects of the mid-gap defect state on the material's optical characteristics. The anneal process returns the real part index to its baseline dispersion while retaining an onset of absorption starting at the defect level $E_{A}$ = 1.8 eV, signifying a stable mid-gap energy transition with a measured state lifetime of $τ _{PL}$ = 2.7 ns. The scalability of this process for producing three-level transition magnetic materials suggests passive optical or magnetooptic devices can be constructed that interconnect photonic and spintronic effects for emerging system designs and potential applications in quantum information.

The effect of structural relaxations on the magnetocrystalline anisotropy energy (MAE) was investigated by using density functional theory (DFT). The theory of the impact of magnetostructural coupling on the MAE was discussed, including the effects on attempt frequency. The MAE for ferromagnetic FePt (3.45 meV/formula unit) and antiferromagnetic PtMn (0.41 meV/formula unit) were calculated within the local density approximation (LDA). The effects of the structural relaxation were calculated and found to give a

This work is devoted to the study of the magnetic properties and Electron Paramagnetic Resonance (EPR) spectroscopy of TiO2:Fe nanoparticles doped with Al in different structural states. The sol-gel methods have been used to obtain the particles in both crystalline (average size from 3 to 20 nm) and X-ray amorphous states. The electron paramagnetic resonance spectra of crystalline samples TiO2:Fe doped with aluminum besides a resonance line with g-factor ~2 exhibit a small signal with a g-factor of 4.3 from Fe3+ ions with rhombohedral distortions. The fraction of Fe3+ with rhombohedral distortions increases with increasing aluminum content. For the amorphous state at Al doping, the resonance with a g-factor of 4.3 is completely dominant in the electron paramagnetic resonance spectrum. The density functional theory calculation shows that aluminum prefers to be localized near iron ions, distorting the nearest Fe3+ environment. The complex integral electron paramagnetic resonance spectrum of all samples was fitted with sufficient accuracy by three separate resonance lines with different widths and intensities. The temperature behavior of the electron paramagnetic resonance spectrum can be described by the coexistence of paramagnetic centers (isolated Fe3+ ions including dipole-dipole interactions) and iron clusters with negative exchange interactions.

Nanosheets composed of stacked atomic layers exhibit unique magnetic, electrical, and electrochemical properties. Here, we report the effect of iron substitution on the structure and magnetism of nickel hydroxide, Ni(OH)2, nanosheets. Ni(OH)2 and iron-substituted Ni(OH)2 (5, 10, 20, and 50 atomic % Fe substitution) were synthesized using a rapid microwave-assisted hydrothermal process. Scanning and transmission electron microscopy show the materials are polycrystalline nanosheets that aggregate into micron-sized clusters. From X-ray diffraction characterization, iron substitutes into the α-Ni(OH)2 lattice up to 20 at. % substitution. The nanosheets exhibit different in-plane and through-plane domain sizes, and Fe substitution affects the nanocrystallite shape anisotropy. The magnetic response differs with Fe substitution: 0% and 5% Fe are ferromagnetic, while samples with 10% and 20% Fe are ferrimagnetic. The competing interactions between magnetization sublattices and the magnetic anisotropy due to the crystalline and shape anisotropy of the nanosheets lead to magnetization reversal at low temperatures. The correlation between higher coercivity and larger nanocrystalline size anisotropy with higher Fe % supports that magnetic anisotropy contributes to the observed ferrimagnetism. The interplay of morphology and magnetic response with Fe-substituted Ni(OH)2 nanosheets points to new ways to influence electron interactions in layered materials which has implications for batteries, catalysis, sensors, and electronics.

Glassy nanocomposites containing Yb3+/Er3+-doped GdF3 and LiGdF4 nanocrystals have been prepared by controlled crystallization of the xerogel and the structural, up-conversion luminescence, and magnetic properties were analyzed and discussed. Structural and morphological analysis showed uniform distribution of both GdF3 and LiGdF4 nanocrystals (tens of nm size), embedded in silica glass matrix as the result of thermal decomposition of the trifluoracetates, revealed as a strong exothermic peak at about 300 °C; the Li-ions co-doping showed a strong influence on the GdF3 and LiGdF4 nanocrystalline fraction. The energy dispersive spectrometry mapping showed Gd, F and Yb, Er within the nanocrystals but not in the silica glass matrix. X-ray diffraction pattern analysis indicated the crystalline lattice distortion consistent with the Yb/Er incorporation in both fluoride nanocrystals. The “green” ((2H11/2, 4S3/2) →4I15/2) and “red” (4F9/2→4I15/2) up-conversion luminescences at 525, 545, and 660 nm observed under 980 nm laser light pumping were assigned to the Er3+ ions deexcitation through a two-photon process. The magnetic properties of the nanocomposite are strongly temperature dependent. The magnetization hysteresis loops show a ferromagnetic behavior at low temperatures (5K) related to the rare-earth ions contribution and the saturation magnetization of 39 emu/g. At 300 K a paramagnetic behavior was observed that was ascribed to the non-interacting localized nature of the magnetic moment of the rare-earth ions. Hence, such novel, multifunctional magnetic and optical materials can allow the intertwining between magnetism and photonics and might offer new opportunities for new magneto-optical device development.

Oxygen vacancies and lattice oxygen on the surface of nanoparticles play crucial roles in the magnetism of transition metal oxides. A fundamental understanding of the interactions between the 2p or...

The electronic and magnetic characteristics of two-dimensional materials have been the focus of attention in order to a wider range of spintronic applications. By using first-principles calculations, H atomic adsorption converts single-layer FePS3 from semiconductor to half-metal while Li makes it to metal. We also find that the magnetic ground state of intrinsic FePS3 can be converted from antiferromagnetic to ferromagnetic by adsorbing H atoms, while alkali-metal atoms have no effect on it. Furthermore, the magnetic ground state is found sensitive to the numbers of H adatom on the surface of FePS3 and demonstrates a vibration behavior. The present findings regarding a surface-adsorption-tuned bandgap and magnetism controlled by the adsorption concentration in a two-dimensional van der Waals magnets could lead to potential applications in next-generation magnetic memory storage, sensors and spintronic.

Magnetism of materials may be adjusted by varying the adjacent magnetic ions in materials, such as Ru4+ in SrRuO3. We here report a study of the structure, electro-transport and magnetic properties of poly-crystallized SrRuxO3, which is synthesized by solid-state reaction. Results show that all the synthesized SrRuxO3 samples remain the single phase, and the grain size increases with increasing the Ru content. A semiconducting behavior with x ≤ 1 and a Fermi Liquid behavior with x > 1 are observed and determined. At 10 K, the saturated magnetic moment increases with x from 21.02 to 29.82 (emu/g), while the coercivity decreases from 5100 to 910 (Oe), which are also confirmed by the first principle calculations.

Using a simple dipping method, a novel the magnetically driven hydrophobic polyurethane sponge (MHPS) was synthesized in this work. The isodecyl alcohol with longer carbon chain is grafted onto the sponge surface through substitution reaction and condensation reaction, and Fe3O4 nanoparticles are adhered to the sponge to give it magnetism and make it easy to collect. MHPS were characterized by Fourier transformed infrared, X-ray diffraction, scanning electron microscopy and energy dispersive spectrometers. The maximum adsorption capacity for various oils/organic solvents was 24–50 times its own weight. MHPS shows excellent reusability after ten absorption–extrusion-heating cycles. Moreover, it can selectively absorb and continuously remove oil in a wide range of water due to the combination of its high porosity, hydrophobicity and lipophilicity. The magnetism of MHPS makes it easy to collect with magnets. It is believed that MHPS has potential application prospects in oil purification and oil spill removal industry wastewater.

International audience; With their high chemical and self-irradiation stability, crystalline monazites are among the most promising materials for the encapsulation of nuclear wastes. Yet, the local and magnetic structures of the matrices doped with low-content actinide cation, depicted as most resistant, are still unclear. This limits the development of theoretical approaches predicting their behavior under extreme conditions—self-irradiation and long-term leaching. Here, we characterize the model matrices La1–xMxPO4 (0 ≤ x ≤ 0.10)—with M = Sm, 239Pu, 241Am—by X-ray diffraction and solid-state 31P NMR. As an example, we confirm that La0.96241Am0.04PO4 has higher self-irradiation resistance compared to 241AmPO4. Further, computational analyses show that magnetic properties of the Pu complex are strongly affected by the J-mixing and the paramagnetic NMR shifts are dominated by the Fermi contact contribution, arising from delocalization of the spin density of the cation toward the phosphorus through the bonds.

In this study, we adopted a simple strategy of the arc discharge to prepare the B-doped SiC microwave nano-absorbers. Herein, the amorphous boron was selected as a doping B element source to tune the electromagnetic parameters of the SiC nanopowders. The experimental results indicate that the doping B in the SiC can conveniently tailor the microwave absorption capability of the SiC nanopowders. The appropriate doping B in the SiC can contribute to excellent synergistic effects among its defect dipoles, leakage, and magnetism. Among the doped SiC with B doping content of 0, 5, 10, and 15 at.%, the SiC with doping B content of 10 at.% acquired the optimized impedance matching and enhanced microwave absorption properties. And the optimal reflection loss (RL) value − 51.2 dB at 6.76 GHz with a matching thickness of 2.9 mm is acquired. The RL of the B-doped SiC nanopowders with B doping content of 10 at.% exceeding − 10 dB is about 3–5 times those of the other three samples in the ranges of 1–18 GHz at a matching thickness of 1.2–6.0 mm. Therefore, this work provided a feasible way to tune the microwave absorption properties of the B-doped SiC, which is of great significance to improve SiC-based high-temperature dielectric ceramics of microwave absorption performances by the defect-engineering strategy.

MOLLYNX is a new crystallographic tool developed to access a more precise description of the spin-dependent electron density of magnetic crystals, taking advantage of the richness of experimental information from high-resolution X-ray diffraction (XRD), unpolarized neutron (UND) and polarized neutron diffraction (PND). This new program is based either on the well known Hansen–Coppens multipolar model (MOLLYNX-mult) or on a new expansion over a set of atomic orbitals (MOLLYNX-orb). The main difference between the two models is the basis of the expansion: in MOLLYNX-mult the expansion is over atom centered real spherical harmonics, in MOLLYNX-orb the expansion is over a set of atomic orbitals with which mono and bicentric contributions are calculated. This new approach of MOLLYNX-orb can also be applied to nonmagnetic crystals. This paper summarizes the theoretical ground of two models and describes the first applications to organic, organometallic and inorganic magnetic materials

Magnetic phase coexistence in the substituted perovskite compound, La0.4Bi0.3Sr0.3MnO3, is attributed to the spontaneous moment and a step-like metamagnetic transition observed in the magnetization measurements in its magnetically order state. The magnetism of samples reduced to nanometer sizes by the “top down” approach exhibits interesting changes with respect to the bulk, thus giving a handle in influencing the physical properties by reducing the particle size. The bulk sample orders ferromagnetically at TC = 295 K, whereas in nano-sized samples with particle sizes in the range of 21–30 nm, even though TC does not change, the transitions are suppressed. The nano-sized powder samples show a broad hump in the plot of magnetic susceptibility, signifying the possible disordered antiferromagnetic state. A systematic decrease in the magnitude of magnetization in nano-sized samples shows that the reduction in magnetic interaction could be attributed to the formation of a magnetic dead layer around the magnetic core.

We successfully fabricated ZnO, Zn0.96Co0.04O, Zn0.95Co0.04Ce0.01O, Zn0.94Co0.04Ce0.02O, and Zn0.92Co0.04Ce0.04O nanoparticles and studied their room-temperature structure and magnetic properties. The X-rays diffraction (XRD) patterns of all the samples confirmed the presence of a wurtzite-type structure. XRD and Transmission Electron Microscopy (TEM) results showed that Zn2+ ions originally at tetrahedral sites were replaced by high-spin Co2+ and Ce3+ ions. This study also showed that with an increase in co-dopant concentration, the average grain size of the samples increased. We found that Zn0.96-xCo0.04CexO (x = 0.0, 0.1, 0.2, and 0.4) nanoparticles were ferromagnetic with a Curie temperature above 300 K. In addition, a large increase in ferromagnetism, i.e., high coercivity field, Hc, of 90Oe and remanent magnetization, Mr, of 0.25 × 10−2 emu/g, was observed for Zn0.96-xCo0.04CexO (x = 0.2) nanoparticles. The origins of ferromagnetism may be either due to the intrinsic nature of Co and Ce co-doped samples or to the presence of certain undetected spinel-type impurities in the samples. Also, it was concluded that Co and Ce incorporation are responsible for ferromagnetism in the doped sample. The doping generates oxygen vacancies, which trap charges and cause a rise in F-centers, resulting in exchange interactions with impurity atoms and increased magnetism. All these results showed that co-doped ZnO-based diluted magnetic semiconductors could be considered for spin-based electronics and optoelectronics devices.

BiFeO3 has been recognized as one of the most important room-temperature single-phase multiferroic materials, but it still suffers from several drawbacks especially the weak magnetoelectric coupling. In the present work, the electric-field-controlled magnetism is achieved in Bi1-xGdxFeO3 system, which involves a field-induced transition of Pna21/R3c at the morphotropic phase boundary region, and the magnetic state is switched between cycloidal state and canted antiferromagnetic state. The electric-field-controlled magnetism becomes reversible with the help of annealing, which is confirmed by magnetic hysteresis loops and the quantitative ratio of the involved phases for the as-sintered, as-poled and as-annealed samples. Compared with the systems of Bi1-xNdxFeO3 and Bi1-xSmxFeO3, it is easier to tune the symmetry from R3c to Pna21 with lower rare earth-content, and the field-induced transition is more apparent and subsequently leads to more significant electric-field-controlled magnetism in a wider composition range.

We present a refinement of the widely accepted spin-wave spectrum that Kalinikos and Slavin (Kalinikos, 1981; Kalinikos and Slavin, 1986) computed for magnetic films with an in-plane magnetization. The spin wave spectrum that follows from the diagonal approximation in this theory becomes inaccurate for relatively thick films, as has already been noted by Kreisel et al. (2009). Rather than solving an integrodifferential equation which follows from the magnetostatic Green's function, as done by Kalinikos and Slavin (Kalinikos, 1981; Kalinikos and Slavin, 1986), we impose the exchange and magnetostatic boundary conditions on bulk spin-wave solutions. This boundary problem has an accurate analytical solution which is quantitatively different from the commonly used diagonal theory (Kalinikos, 1981; Kalinikos and Slavin, 1986) for magnetic films.

Electric field (E-field) control of magnetism based on magnetoelectric coupling is one of the promising approaches for manipulating the magnetization with low power consumption. The evolution of magnetic domains under in-situ E-fields is significant for the practical applications in integrated micro/nano devices. Here, we report the vector analysis of the E-field-driven antiparallel magnetic domain evolution in FeCoSiB/PMN-PT(011) multiferroic heterostructures via in-situ quantitative magneto-optical Kerr microscope. It is demonstrated that the magnetic domains can be switched to both the 0° and 180° easy directions at the same time by E-fields, resulting in antiparallel magnetization distribution in ferromagnetic/ferroelectric heterostructures. This antiparallel magnetic domain evolution is attributed to energy minimization with the uniaxial strains by E-fields which can induce the rotation of domains no more than 90°. Moreover, domains can be driven along only one or both easy axis directions by reasonably selecting the initial magnetic domain distribution. The vector analysis of magnetic domain evolution can provide visual insights into the strain-mediated magnetoelectric effect, and promote the fundamental understanding of electrical regulation of magnetism.

In recent years, layered metal dichalcogenides (LMDs) have drawn extensive attention in fundamental research field due to their unique electronic, mechanical, and optical properties. In addition, magnetic two-dimensional LMDs are considered as a promising candidate for the next-generation spintronic devices. The nonmagnetic property of common SnS2 nanopowders has hampered its applications in spintronics. Doping is an effective way to change the intrinsic properties of non-magnetic semiconductor materials. Pure SnS2 and Mn-doped SnS2 were prepared by the hydrothermal method. In this study, undoped SnS2 has diamagnetism, which is caused by lattice fluctuation. The magnetic property of SnS2 was obviously enhanced after doped with a small amount of Mn2+. The results of VSM investigation showed the enhanced paramagnetism of Mn-doped SnS2 and weak ferromagnetism as well. It was deduced that the joint effect of the intralayered and interlayered Mn atoms led to the changes in the magnetic properties. Although the magnetism of the samples has been enhanced, the XRD patterns indicated that the crystal structure had not been changed by doping. This work suggested that Mn-doped SnS2 has potential applications in spintronic devices.

Single-crystal growth of rutheno-cuprate materials EuSr2RuCu2O8−δ (RuEu-1212) and (Eu, Ce)2Sr2RuCu2O10−δ (RuEu-1222), where RE denotes a rare-earth element, remains a major challenge, especially for Eu-substituted RuEu-1212 and RuEu-1222 systems, which require removing the magnetic effect of Gd to investigate coexistence of superconductivity on CuO2 and magnetism of Ru. In this study, RuEu-1212 and RuEu-1222 single crystals are prepared via the partial melting technique. The maximum size of grown single crystals of RuEu-1212 was 80 $$\mu$$ m, which is five times larger than in previous studies. Although superconductivity disappeared in the large crystals, a magnetic transition due to Ru was observed at 130–140 K. Meanwhile, platelike RuEu-1222 single crystals with a length of 30 $$\mu$$ m were successfully prepared. After optimizing the sintering conditions, the onset temperature of superconducting transition (Tc-onset) reached close to 40 K and diamagnetism was observed below 20 K, which is almost consistent with the offset temperature of the superconducting transition (Tc-offset) value from the resistance–temperature (R–T) characteristics. The initial magnetization curve at 5 K shows diamagnetism clearly. The Tc-onset and Tc-offset values were 44.3 K and 22.5 K, respectively, which are the highest values of any rutheno-cuprates synthesized by partial melting to date.

This paper has focused on investigating the structure, dielectric, and magnetic characteristic of Sn-ZnO nanopowder with Sn (x = 0%, 2%, 4%, and 6%) synthesized by the co-precipitation technique. Our objective was to obtain the material of low dielectric constant, high electrical conductivity, and magnetism. X-ray diffraction confirmed the Sn-ZnO nanoparticles have a ZnO-like hexagonal structure. It is found that the dielectric constant, dielectric loss, and a.c conductivity of doped nanoparticles were frequency-dependent. The dielectric constant of all the doped samples were increased by the increase in the Sn-doped concentration, while the decrease in frequency increased the dielectric constant and loss. Moreover, the a.c conductivity was increased by the increase in Sn concentration and frequency. Ferromagnetism was observed in ZnO doped with 4% and 6% Sn at room temperature. In addition, a robust magnetic hysteresis loop was observed for doped with 4% Sn to ZnO nanopowder at 300 K with coercive field (Hc) ~ 49 Oe and remnant magnetization (Mr) ~ 0.189 emu/g. The loss of magnetism at higher Sn- ZnO nanopowder was assigned to the suppression of ferromagnetism through paramagnetic interactions. The experimental results showed that 4% Sn- ZnO became ferromagnetic, its lattice shrink and size decreased, which is important for excellent magnetic properties and electrical conductivity. These types of materials have a large number of applications in high-frequency devices, ultrahigh dielectric material gas sensors, spintronics, and optoelectronics.

The structural, magnetic, dielectric, and surface morphology of BiSnxFe1-xO3 (x = 0.0 to 1.0) was analyzed experimentally. The samples were synthesized by a simple chemical micro-emulsion method. The X-ray diffraction (XRD) analysis reveals structural distortion at A site and B site of BFO due to Sn doping in rhombohedral phase. The EDX data certify Sn is well incorporated in BiFeO3. The effect of Sn doping on crystal size and grain size has also been addressed. The FTIR analysis elaborates absorption at 555 cm−1 which is due to stretching and bending vibrations of O–Fe–O bonds. The magnetic properties are illustrated by vibrating sample magnetometer (VSM). The magnetic moments and exchange mechanism described theoretically by DFT analysis which support the experimental results. The dielectric behavior of studied materials has been evaluated by dielectric constant (ɛʹ), tangent loss (tanδ), real and imaginary part of impedance, and Cole–Cole plots in 1–3 GHz. The spin-orientated magnetism and dielectric response increase their potential for microwave absorber and sensor.

The electronic structure and magnetism of Mn2SnS4 are analysed with full-potential first-principles calculations. In order to understand the possible influence of magnetic structure, we have performed calculations of total energies for both ferromagnetic (FM) and antiferromagnetic (AFM) orderings. Antiferromagnetic ordering is of three types. Our computed results reveal that Mn2SnS4 exhibits an AFM-I type antiferromagnetic ordering. The exchange interaction parameters, which reflects the electrostatic Coulomb repulsion of electrons on neighboring atoms and the Pauli principle, were estimated to be J1 = − 14.1 meV, J2= − 5.3 meV and J3 = − 8.2 meV according to the Heisenberg model. It was shown that all values are negative and J1 has the highest absolute value, demonstrating strong antiferromagnetic pairing dominating between the nearest magnetic Mn ions and weak antiferromagnetic coupling within the next-nearest Mn ions. The position of the sulfur atoms have no impact on the values of the aforementioned energies, which validates that the magnetism in Mn2SnS4 is dominated mainly by direct exchange. The associated energy differences involving spin orderings can be used to evaluate the critical temperature of the compounds Mn2SnS4. Our calculations show that taking into account the spin–orbit coupling has no significant effect on the accuracy of the band gap of Mn2SnS4. The calculated results of equilibrium volume, antiferromagnetic ordering type, local magnetic moment, and band gap are in good agreement with reported experimental results. The relative differences between spin configurations can be used to derive observables such as Curie-Weiss temperature (θ). The Curie-Weiss temperature is calculated using the mean-field approximation. Reasonable agreement with the experiment is found for all properties including the equilibrium volume, local magnetic moment, antiferromagnetic ordering type, band gap, and the Curie-Weiss temperature.

We investigate numerically and experimentally the optical properties of the transverse electric (TE) waves supported by a dielectric-metal heterostructure. They are considered as the counterparts of the surface plasmon polaritons (i.e., the transverse magnetic (TM) waves) which have been extensively studied in the last several decades. We show that TE waves with resonant wavelengths in the visible light spectrum can be excited in a dielectric-metal heterostructure when the optical thickness of the dielectric layer exceeds a critical value. We reveal that the electric and magnetic field distributions for the TE waves are spatially separated, leading to higher quality factors or narrow linewidths as compared with the TM waves. We calculate the thickness, refractive index and incidence angle dispersion relations for the TE waves supported by a dielectric-metal heterostructure. In experiments, we observe optical resonances with linewidths as narrow as ∼10 nm in the reflection or scattering spectra of the TE waves excited in a Si3N4/Ag heterostructure. Finally, we demonstrate the applications of the lowest-order TE wave excited in a Si3N4/Ag heterostructure in optical display with good chromaticity and optical sensing with high sensitivity.

Despite being difficult to identify, extremely dilute oxygen vacancies have been widely reported to play an important role in enhancing magnetism in ZnFe2O4. The mechanisms underlying this enhanced magnetism have not been well understood for a long time and remain controversial because the formation of oxygen vacancy-rich ZnFe2O4 can be accompanied by changes in the chemical/physical characteristics, especially the composition, particle size, surface morphology and cation distribution, which can significantly affect the magnetization. An open and important question is whether and to what extent the enhanced magnetization can be attributed only to oxygen vacancies. In this study, the relationship between the magnetization and oxygen vacancies in ZnFe2O4 was definitively determined by using a carefully designed “shake-and-heat” treatment to prepare vacancy-rich samples while keeping the other crystal/surface parameters constant. Compared to the nearly vacancy-free paramagnetism samples, the vacancy-rich samples exhibited a higher magnetization of approximately 5 emu/g at both 300 K and 2 K. The Fe3+-O2--Fe3+ superexchange paths broken by oxygen vacancies then resulting in the Fe3+-Fe3+ ferromagnetism configuration. Meanwhile, the oxygen vacancy is highly diluted then the ferromagnetism configuration is confined in a single super-cell, favoring a short-range magnetic ordering at room temperature. The concentration of oxygen vacancies was calculated to be 0.68% by magnetization measurement. Our results may shed a light on how oxygen vacancies affect magnetism.

In this paper, a simple, reproducible and cost-effective solid-state reaction sintering process is developed to fabricate (K0.5Na0.5)NbO3-xBaNi0.5Nb0.5O3-δ (KNN-xBNN) ceramics with a narrow bandgap and room-temperature ferromagnetism. Here, we report a systematic investigation of the influence of the BaNi0.5Nb0.5O3-δ (BNN) concentration on the properties of KNN-xBNN ceramics. All ceramics form orthorhombic perovskite structures with a space group Amm2 and a weak peak at the wavelength of 550 cm−1 that is characteristic of the pillow shoulder of the orthorhombic phase. KNN-xBNN ceramics with x between 0.02 and 0.08 have a narrow bandgap of about 2.5 eV—much smaller than the 3.5 eV of its parent (K0.5Na0.5)NbO3 (KNN) ceramic—which is attributed to Ni2+-oxygen vacancy combinations (Ni2+-VO) raising the valence electron energy level of the KNN ceramic. Furthermore, doping BNN into KNN ceramics can significantly convert the magnetism from diamagnetism to ferromagnetism and the component of x = 0.08 achieves both maximum saturation magnetisation intensity (14 memu/g) and minimum coercive magnetic field (80 Oe). Our findings provide a systematic insight into the bandgap tunability and ferromagnetism induction at room temperature in lead-free perovskite KNN-xBNN ceramics, as well as demonstrate their potential applications in perovskite solar cells and multiferroic devices.

Magnetic nanoparticles are one of the most important and widely used types of nanomaterials, whose unique properties make them special compared to other nanostructures. These particles can be used in various fields. But their role in biomedicine, especially in the field of drug delivery, is significant because their inherent magnetism facilitates many tasks, including targeting, which is very important and necessary in drug delivery. In the present article, an attempt has been made to give general information about magnetic nanoparticles and the properties of particles in biomedical applications. In the following, special attention has been paid to the properties of these particles in drug delivery and their various applications have been studied. The importance of coating magnetic nanoparticles has also been mentioned as a basic requirement for medical applications. In the following, the method of drug loading in magnetic nanoparticles, the entry of particles into the body, targeting, and drug release are discussed, and finally, a brief discussion is presented regarding the pharmacokinetics of drugs and their toxicity in the body.

Titanium disulfide TiS$_2$, which is a member of the layered transition-metal dichalcogenides with the 1T-CdI$_2$-type crystal structure, is known to exhibit a wide variety of magnetism through intercalating various kinds of transition-metal atoms of different concentrations. Among them, Fe-intercalated titanium disulfide Fe$_x$TiS$_2$ is known to be ferromagnetic with strong perpendicular magnetic anisotropy (PMA) and large coercive fields ($H_\text{c}$). In order to study the microscopic origin of the magnetism of this compound, we have performed X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements on single crystals of heavily intercalated Fe$_x$TiS$_2$ ($x\sim0.5$). The grown single crystals showed a strong PMA with a large $H_\text{c}$ of $\mu_0H_\text{c} \simeq 1.0\ \text{T}$. XAS and XMCD spectra showed that Fe is fully in the valence states of 2+ and that Ti is in an itinerant electronic state, indicating electron transfer from the intercalated Fe atoms to the host TiS$_2$ bands. The Fe$^{2+}$ ions were shown to have a large orbital magnetic moment of $\simeq 0.59\ \mu_\text{B}\text{/Fe}$, to which, combined with the spin-orbit interaction and the trigonal crystal field, we attribute the strong magnetic anisotropy of Fe$_x$TiS$_2$., Comment: 24 pages, 8 figures

The spinel ZnFe2O4 specimens were obtained via a hydrothermal and a ceramic method, respectively, and their structural and magnetic properties were comparatively studied. It was found that all the specimens exhibited a single-phase and mixed spinel structure. The magnetism of specimens synthesized via the hydrothermal method is obviously greater than that of specimen prepared via the ceramic method. This can be ascribed to the occupancy of Fe ions resulted from the loss of Zn during the hydrothermal process.

Even though there has been a lot of studies on the magnetic properties of Fe x TiS2 and their corresponding atomic structures at different Fe concentrations, the dependency of the properties on the Fe atomic arrangement has not been fully clarified yet. In this study, Fe x TiS2 structures, synthesized by chemical vapor transport technique at Fe concentrations of 0.05, 0.10, 0.15, 0.20 0.25 and 0.33, were observed three-dimensionally using a transmission electron microscope and their corresponding magnetization values were measured using a superconducting quantum interference device. The results show a switch from local in-plane two-dimensional (2D) ordering of \sqrt 3 a and 2a at concentrations below 0.15 to three-dimensional (3D) ordering of 2a × 2a × 2c at x = 0.20 and 0.25, as well as \sqrt 3 a × \sqrt 3 a × 2c superstructures at x = 0.33, although it should be noted that the x = 0.20 sample only had partial ordering of Fe atoms. The type of Fe ordering present in Fe x TiS2 could be explained by the balance of cohesive energy of neighboring Fe atoms and local strain energy imposed on the host structure due to the formation of Fe clusters. It is also found that the switch from 2D to 3D Fe order coincides with the magnetic measurements, which reveal spin-glass behavior below x = 0.15 and ferromagnetic behavior above x = 0.20. This suggests that the magnetic properties of the Fe x TiS2 structure are highly influenced by the ordering of Fe atoms between planes.

Zn1-xRxO (R = Li, Mg, Cr, Mn, Fe and Cd) were obtained by using co-precipitation synthesis technique with constant weight percent of 3% from R ions. The phase composition, crystal structure, morphology, density functional theory (DFT), and magnetic properties were examined to comprehend the influence of Zn2+ partial substitution with R ions. X-ray diffraction shows that the ZnO lattice parameters were slightly affected by R doping and the doped sample crystallinity is enhanced. Our results show that introducing Cr, Mn and Fe along with Mg into ZnO induces a clear magnetic moment without any apparent distortion in the structural morphology. The spatial configuration of dopant atoms is determined from first-principles calculations, giving a better understanding of the position of the dopant atom responsible for the magnetism. The magnetic moments obtained from our calculations are 3.67, 5.0, and 4.33 μB per dopant atom for Cr, Mn, and Fe, respectively, which agree with the experimental values. While Cr and Fe tend to form clusters, Mn has more propensity to remain evenly distributed within the system, avoiding cluster-derived magnetism.

Magnetoelectric (ME) materials have been attracting extensive attention due to their potential applications. It is important to realize strong ME effect in one single material at sufficiently high temperature, and thus substantial efforts in searching for ME materials with strong ME coupling together and a comprehensive understanding of the underlying mechanism is necessary. Herein we focus on the Mn-doped linear ME material Co4-xMnxNb2O9, in which a large electric polarization driven by magnetic field emerges below its Neel temperature TN, by presenting the detailed characterizations on the structure, magnetism, and ME effect. It is revealed that an increasing Mn substitution x allows largely enhanced TN and gradually suppressed ME coefficient αME. This ME coupling suppression is attributed to the weak spin-orbit interaction of Mn2+ with respect to Co2+. It is indicated that the Dzyaloshinskii-Moriya (DM) interaction plays an important role in the ME coupling. The measured largest αME is found in For Co0.8Mn3.2Nb2O9, reaching up to 9.9 ps/m at 10 K while the TN reaches up to 102 K, exceeding most of the linear ME materials that have been reported.

The magnesium-rich intermetallic ternary compound NdNiMg15 in space group P-4/nmm (no. 26) space group in trigonal phase is studied theoretically using hybrid functional theory (HP-B3PW91) in the density functional theory (DFT) framework. The calculation results are in good agreement with experimental data. The metallic nature of the compound is estimated from the electronic properties. The magnetic as well as metallic character of the compound is due to the Nd 4f electrons. The title compound exhibits good conductivity as revealed by the thermoelectric analysis. The magnetic phase of the material indicates its stability within the G-type antiferromagnetic phase (G-AFM), governed by direct Nd–Nd exchange interactions with a magnetic moment of 3.57µB/Nd per unit cell. The AFM phase of the studied compound is also confirmed by post-DFT measurements at TN = 8.15 K as well as θ = −2.5 K. The antiferromagnetic nature of this compound could enable its use in magnetic probes to read data stored in antiferromagnetic moments while leaving them unaffected by disturbing magnetic fields.

Low-dimensional magnetic materials with high stabilities and outstanding magnetic properties are essential for the next generation of spintronic devices. We will discuss the intrinsic magnetism in ...

In this paper, the crystal structure, vacancy defect, local electron density and magnetic properties of Gd1-xCaxCrO3 (0 ≤ x ≤ 0.3) polycrystalline samples were investigated systematically. The crystal structural analyses show that all the samples are orthorhombic phase and a structural distortion happens around x = 0.3. Due to the formation of Cr4+ ions, both the lattice constant and the Cr–O bond length decrease. The results of positron annihilation spectrum reveals that the vacancy defect concentration increases and the local electron structure changes with the introduction of Ca2+ ions. The field-cooled (FC) and zero-field cooled (ZFC) curves of Gd1-xCaxCrO3 samples measured under H = 100 Oe exhibits negative magnetization characteristics due to the interaction between Gd3+ and Cr3+ ions, and the magnetism can be affected by the structural distortion.

Magnetic nanoparticles have recently attained much interest due to the wide distribution of their applications. The current work is concerned with the synthesis of magnetic iron oxide nanoparticles using green and chemical methods. Licorice extract has been used as the main factor for the production of green synthesized magnetic nanoparticles (GSM), compared with the co-precipitation method for the production of chemically synthesized magnetic nanoparticles (CSM). Both scanning electron microscopy (SEM) and particle size analyzer (PSA) proved the formation of the particles in the nanoscale with the range of 50–110 nm and 40–100 nm for GSM and CSM, respectively. Furthermore, Energy-dispersive X-ray spectroscopy (EDX) indicated the existence of iron and oxygen elements in both the samples and proved the formation of iron oxide nanoparticles. Both types of nanoparticles were solely integrated with chitosan for the formation of magnetic-dependent membranes followed by integration-dependent characterization using SEM and Raman spectroscopy. The tensile properties of the membranes showed higher elongation and strain properties of chitosan/GSM membrane compared with plain chitosan or chitosan/CSM membranes, which candidate it for mechanical-dependent applications. The vibrating sample magnetism (VSM) properties showed that GSM nanoparticles are superparamagnetic. In addition, the GSM nanoparticles are applied as methanol electrochemical sensors with high sensitivity even at low concentrations of methanol.

The antiferromagnetic topological insulator has attracted lots of attention recently, as its intrinsic magnetism and topological property make it a potential material to realize the quantum anomalous Hall effect at relative high temperature. Until now, only MnBi2Te4 is predicted and grown successfully. The other MB2T4-family materials predicted (MB2T4: M = transition metal or rare earth element, B = Bi or Sb, T = Te, Se, or S) with not only antiferromagnetic topological property but also rich and exotic topological quantum states and dynamically stable (or metastable) structure have not been realized on experiment completely. Here, MnBi2Te4 single crystals have been grown successfully by us. It shows typical antiferromagnetic character with Neel temperature of 24.5 K and a spin-flop transition at H ≈ 35,000 Oe, 1.8 K. In order to obtain the other members of MB2T4-family materials, it is necessary to understand the growth mode of MnBi2Te4. Its growth mode may be the layer-inserting growth mode based on symmetry, which is supported by our X-ray photoelectron spectroscopy (XPS) result, as the intrinsic chemical states of Mn and Te of MnBi2Te4 are the same with those of inserting material α-MnTe. Understanding the growth mode of MnBi2Te4 can help us to grow the other members of MB2T4-family materials.

Crystalline iron selenide (Fe3Se4) nanoparticles (NPs) present a useful model system for a fundamental understanding of magnetism apart from having potential applications in permanent-magnet-relate...

Aiming to clarify the mechanisms governing the interlayer magnetic coupling, we have investigated the stacking energy and interlayer magnetism of bilayer CrBr3 systemically. The magnetic ground sta...

Precise tuning of the magnetic states of geometrically frustrated materials remains a critical challenge, as this process will not only promote understanding of fundamental magnetism but also accel...

Moire systems formed by 2D atomic layers have widely tunable electrical and optical properties and host exotic, strongly correlated and topological phenomena, including superconductivity, correlated insulator states and orbital magnetism. In this Viewpoint, researchers studying different aspects of moire materials discuss the most exciting directions in this rapidly expanding field.