Magnetochemistry

M-type Sr_0.1Ca_0.4La_0.5Fe₁₂O₁₉ powder specimens doped with different precursors RFe₂O₄(R = Co, Ni, Cu, Zn, and Mg) were prepared via a traditional solid-state reaction method. The structural and magnetic properties of the specimens were studied. Only nthe single magnetoplumbite phase was found in all the specimens with uniformly distributed particles. The specimen with Zn-type precursor has the highest saturation (M_s), while the specimen with Co-type precursor has the highest remanent magnetism (M_r), coercivity (H_c), and the best comprehensive magnetic properties. Full article

Electrodeposition under magnetic fields (magnetoelectrodeposition; MED) can induce surface chirality on copper films. The chiral signs of MED films should depend on the magnetic field polarity; namely, the reversal of the magnetic field causes the opposite chiral sign. This represents odd chirality for the magnetic field polarity. However, odd chirality was broken in several MED conditions. This paper makes a survey of breaking of odd chirality in the MED conditions such as low magnetic fields, specific adsorption of chloride ions, micro-electrode, and cell rotation. These results indicate that the ordered fluctuation of magnetohydrodynamic micro-vortices induces the breaking of odd chirality and that the random fluctuation results in the disappearance of surface chirality. Full article

Micro-structured copper layers are obtained from pulse-reverse electrodeposition on a planar gold electrode that is magnetically patterned by magnetized iron wires underneath. 3D numerical simulations of the electrodeposition based on an adapted reaction kinetics are able to nicely reproduce the micro-structure of the deposit layer, despite the height values still remain underestimated. It is shown that the structuring is enabled by the magnetic gradient force, which generates a local flow that supports deposition and hinders dissolution in the regions of high magnetic gradients. The Lorentz force originating from radial magnetic field components near the rim of the electrode causes a circumferential cell flow. The resulting secondary flow, however, is superseded by the local flow driven by the magnetic gradient force in the vicinity of the wires. Finally, the role of solutal buoyancy effects is discussed to better understand the limitations of structured growth in different modes of deposition and cell geometries. Full article

FeCoB (25 nm)/Hf($t_{\mathrm{Hf}}$)/FeCoB (25 nm) sandwich films with different hafnium thicknesses $t_{\mathrm{Hf}}$ were fabricated using a modified compositional gradient sputtering method to obtain self-biased high-frequency performances. The effects of $t_{\mathrm{Hf}}$ on the interlayer coupling and FMR frequency were investigated. It is revealed that interlayer coupling enhanced the resonance frequency by 48%, and a ferromagnetic coupling between the FeCoB films occurred for the trilayers with $t_{\mathrm{Hf}}$ < 3.0 nm, likely due to the interface roughness and pinhole effect. In this case, only acoustic mode resonance was observed with the same high-frequency performance as the corresponding FeCoB single layer. In contrast, a $t_{\mathrm{Hf}}$-dependent antiferromagnetic interlayer coupling appeared at $t_{\mathrm{Hf}}$ > 3.0 nm. The coupling coefficient J₁ was antiferromagnetic, and a biquadratic coupling J₂ appeared at t_Hf > 3.5 nm. The coupling mechanism was simulated and verified by Layadi’s rigid model, and the simulation was consistent with the experimental results. Full article

Realizing the high molecular orientation and structurally ordered microstructure of organic semiconductor polymer thin films is beneficial for enhancing the charge transport of conjugated polymers and achieving high-performance organic electronic devices. In this work, we successfully developed large-area highly aligned films of a thiophene-based polymer, namely poly(2,5-bis(3-alkylthiophen-2-yl) thieno [3,2-b] thiophene) (PBTTT), using the magnetic alignment method at a low magnetic field (0.12 T), which was assisted by superparamagnetic nanoparticles Fe₃O₄@C. The aligned microstructure of the composite films is confirmed by systematic analysis that includes polarized optical microscopy, polarized UV–visible absorption spectroscopy, and an atomic force microscope. Organic field effect transistors based on magnetic aligned composite film exhibit a 2.8-fold improvement in carrier mobility compared with the unaligned films. We hold a formation mechanism that the rapid magnetically induced self-assembly property of Fe₃O₄@C and its intermolecular interaction with polymer chains are key to the new method of preparing oriented thin films. Full article

The magnetic nanoparticles (MNPs) with decreasing heating efficiency (characterized by specific loss power, SLP) with temperature increase, especially around the Curie temperature (T_C), are expected to realize the self-regulated temperature hyperthermia of the tumor. However, the actual decrease of the SLP is gradual, resulting in the deviation of self-regulated temperatures from the measured T_C. So far, no method is available for evaluating the heating performances of those MNPs. Here, by simulating the temperature-dependent SLP, the heating performances of MNPs are evaluated from three clinically concerning aspects: the capacity for effective heating, the temperature uniformity in the tumor, and the temperature stability under environmental changes such as MNP loss or tumor progression. The developed methods were applied to ZnCoCrFeO, Fe₃O₄, and γ-Fe₂O₃ MNPs. It was found that the uniform temperature distribution relies on lowering the heating power in the inner regions of the tumor, and the stable control of temperature depends on the dynamic adaptation of the heating power to the tumor temperature change. The proposed method may be used to predict the heating ability of MNPs and help the selection of MNPs for hyperthermia. Full article

Calcium phosphate coatings were formed on a Ti6Al4V substrate by electrodeposition under a high magnetic field up to 16 T. The magnetic field was parallelly applied to the vertical surface electrode. Changes in crystal morphology of calcium phosphates were investigated as a function of the magnetic field amplitude, and the results are discussed in terms of magnetic field effects. Magnetohydrodynamic convection due to the Lorentz force could considerably reduce the formation of volcano-like structures and generate more uniform deposits without changing Ca/P ratios. Full article

The major aim of the current investigations is to study the magnetohydrodynamic effects on heat and mass transfer phenomena in third-grade fluid past an inclined exponentially stretching sheet fixed in a porous medium with Darcy–Forchheimer law influence. The constitutive equations compatible for heat and mass transportation in third-grade fluid in terms of partial differential equations are modeled. These partial differential equations are then converted to ordinary differential equations by using suitable similarity variables formulation. The transformed flow model is solved by using MATLAB built-in numerical solver bvp4c. Effects of pertinent parameters on physical properties that are velocity field, temperature field and mass concentration along with skin friction coefficient, Nusselt number and Sherwood number are demonstrated in graphs and tables. The impact of dimensionless numbers on the physical properties is analyzed and discussed with a physical view point at angle $\alpha =\pi /6$ (inclined sheet). It is seen that as the third-grade fluid parameter $\left(0.1\le \beta \le 11\right)$ is increased, the velocity profile increases, but the temperature field and mass concentration are decreased. It is observed that as the permeability parameter $(1\le K^{*}\le 11)$ is raised, the velocity distribution decreases and mass concentration increases. It is concluded from the results that owing to an increase in the local inertial coefficient $\left(0.1\le Fr\le 5\right)$, the velocity profile reduces but an increment in mass concentration is noted. It is concluded that by increasing values of magnetic field parameter $\left(0.1\le M\le 10\right)$ the velocity field is delineated and temperature field is elevated exactly according to the physics of magnetic field parameters. The present results are compared with already published results and it is observed that there is good agreement between them. This good agreement ensures the validation of accuracy of the results. Full article

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components. Full article

The pressure–temperature phase diagram of the multiferroic TbFe${}_{2.46}$Ga${}_{0.54}$(BO${}_3$)${}_4$ was studied for hydrostatic pressures up to 7 GPa and simultaneously with temperatures up to 400 K by the Raman spectroscopy technique. The structural phase transition from the $R32$ phase to the $P{3}_{1}21$ phase was determined by observing the condensation of soft modes and the appearance of new lines. An increase in pressure leads to an increase in the temperature of the structural phase transition. These phases are stable over the entire investigated temperature and pressure range. No other phases have been found. Full article

For single-molecule toroics (SMTs) based on noncollinear Ising spins, intramolecular magnetic dipole–dipole coupling favours a head-to-tail vortex arrangement of the semi-classical magnetic moments associated with a toroidal ground state. However, to what extent does this effect survive beyond the semi-classical Ising limit? Here, we theoretically investigate the role of dipolar interactions in stabilising ground-state toroidal moments in quantum Heisenberg rings with and without on-site magnetic anisotropy. For the prototypical triangular SMT with strong on-site magnetic anisotropy, we illustrate that, together with noncollinear exchange, intramolecular magnetic dipole–dipole coupling serves to preserve ground-state toroidicity. In addition, we investigate the effect on quantum tunnelling of the toroidal moment in Kramers and non-Kramers systems. In the weak anisotropy limit, we find that, within some critical ion–ion distances, intramolecular magnetic dipole–dipole interactions, diagonalised over the entire Hilbert space of the quantum system, recover ground-state toroidicity in ferromagnetic and antiferromagnetic odd-membered rings with up to seven sites, and are further stabilised by Dzyaloshinskii–Moriya coupling. Full article

During the explosion of energetic materials, electromagnetic interference is generated, which can affect the normal operation of surrounding electronic equipment. Therefore, an electromagnetic radiation measurement device based on a short-wave omnidirectional antenna and ultra-wideband omnidirectional antenna was designed to measure the electromagnetic radiation generated by the explosion of energetic materials of different masses, and the electromagnetic radiation characteristics were obtained through data processing. The results showed that the electromagnetic signal can still be collected hundreds of milliseconds after the explosive is detonated, and the electromagnetic radiation generated by the explosion is continuous and intermittent, which is a phenomenon that has not been found in this field at present. The mass of the energetic material had a significant effect on the time-domain characteristics of the electromagnetic radiation generated by the explosion: the higher the mass of the energetic material was, the shorter the delay response of the electromagnetic signal was, the longer the duration was, and the earlier the peak appeared. The frequency of electromagnetic radiation signals generated by the explosion of energetic materials was mainly concentrated below 100 MHz, and the energy was most concentrated in the frequency band of 0~50 MHz. The composition of energetic materials had the greatest influence on the spectral distribution, and the spectral distribution of electromagnetic radiation produced by the explosion of explosives with different compositions had obvious specificity. The electromagnetic radiation intensity generated by the explosion of energetic materials had a strong correlation with the distance from the explosion center, and it significantly decreased as the distance increased. The structure and detonation method of energetic materials changed the geometrical motion pattern during the explosion, resulting in the non-uniformity of electromagnetic radiation propagation. Full article

Magnetic multilayer with large perpendicular magnetic anisotropy (PMA) has attracted sustained interest owing to its importance to fundamental physics and applications. In this work, the high quality of Pt/Co/Pt heterostructures with large PMA was successfully achieved to exhibit a large anomalous Hall effect (AHE) with squared Hall loops. By calculating the proportional relationship between the longitudinal resistivity $({\rho }_{xx})$ and the abnormal Hall coefficient (R_s), it is confirmed that the basic mechanism of AHE comes from the external skew scattering (SS) and side jump (SJ), while SS contribution, related to asymmetric scattering from impurities, is dominant in the AHE. Furthermore, the obvious magneto-optical Kerr effect (MOKE) was also observed using the polar MOKE microscopy. The obviously circular magnetic domain can form and propagate in response to the applied out-of-plane magnetic field, resulting in the magnetization reversal of the entire film. This work offers important information in terms of both AHE and MOKE in the ultrathin ferromagnetic films with perpendicular anisotropy, establishing the application foundation for the nonvolatile memories and spintronics. Full article

Antidot lattices made of magnetic thin films are good candidates to be employed in future magnetic recording media. In this manuscript we present a study on the effect of shape and field-induced magnetic anisotropies on the magnetization reversal of 10 nm and 50 nm thick permalloy antidot lattices. Rounded antidot square lattices were fabricated using a combination of electron beam evaporation and laser interference lithography, covering surfaces of a few cm². We demonstrate that a magnetic anisotropy induced in the samples, as a consequence of an applied magnetic field during growth, competes with the shape anisotropy that dominates the response of the patterned thin films, and that the effect of the field-induced magnetic anisotropy scales with the thickness of the antidot thin films. Finally, we have quantified the anisotropy constant attributable to the uniaxial field-induced magnetic anisotropy in our antidot lattices. These findings are supported by micromagnetic simulations performed using MuMax3. Full article

Magnetic nanoparticles (MNPs) have great potential in the drug delivery area. Iron oxide (Fe₃O₄) MNPs have demonstrated a promising effect due to their ferrimagnetic properties, large surface area, stability, low cost, easy synthesis, and functionalization. Some coating procedures are required to improve stability, biocompatibility, and decrease toxicity for medical applications. Herein, the co-precipitation synthesis of iron oxide MNPs coated with four types of primary surfactants, polyethylene glycol 2000 (PEG 2000), oleic acid (OA), Tween 20 (Tw20), and Tween 80 (Tw80), were investigated. Dynamic light scattering (DLS), ζ-potential, and transmission electron microscopy (TEM) techniques were used for morphology, size, charge, and stability analysis. Methylene blue reactive oxygen species (ROS) detection assay and the toxicity experiment on the lung adenocarcinoma A549 cell line were conducted. Two loading conditions for anticancer drug doxorubicin (DOX) on MNPs were proposed. The first one provides high loading efficiency (~90%) with up to 870 μg/mg (DOX/MNPs) drug capacity. The second is perspective for extremely high capacity 1757 μg/mg with drug wasting (DOX loading efficiency ~24%). For the most perspective MNP_OA and MNP_OA_DOX in cell media, pH 7.4, 5, and 3, the stability experiments are also presented. MNP_OA_DOX shows DOX pH-dependent release in the acidic pH and effective inhibition of A549 cancer cell growth. The IC50 values were calculated as 1.13 ± 0.02 mM in terms of doxorubicin and 0.4 ± 0.03 µg/mL in terms of the amount of the nanoparticles. Considering this, the MNP_OA_DOX nano theranostics agent is a highly potential candidate for cancer treatment. Full article

Water electrolysis is one of the most common methods to produce hydrogen gas with high purity, but its application is limited due to its low energy efficiency. It has been proved that an external magnetic field can reduce energy consumption and increase hydrogen production efficiency in water electrolysis. In this study, electrodes with different magnetism were subjected to a perpendicular magnetic field for use in hydrogen production by water electrolysis. Gas bubbles that evolve from the surface of a horizontal electrode detach faster than the bubbles from a vertical electrode. The locomotion of the bubbles is facilitated if the horizontal electrode faces a magnet, which induces the revolution of bubbles between the electrodes. However, the magnetic field does not increase the current density effectively if the electrodes are more than 5 cm apart. A paramagnetic (platinum) electrode has a more significant effect on bubble locomotion than a diamagnetic (graphite) material and is able to increase the efficiency of electrolysis more effectively when a perpendicular magnetic field is applied. The conductivity of platinum electrodes that face a magnet increases if the distance between the electrodes is less than 4 cm, but the conductivity of graphite electrodes does not increase until the inter-electrode distance is reduced to 2 cm. On the other hand, horizontal graphite electrodes that are subjected to a perpendicular magnetic field will generate a higher gas production rate than a platinum electrode without a magnetic field if the inter-electrode distance is less than 1 cm. Full article

This review summarizes the data on the stereochemical structure of functionalized azoles (pyrazoles, imidazoles, triazoles, thiazoles, and benzazoles) and related compounds obtained by multipulse and multinuclear ¹H, ¹³C, ¹⁵N NMR spectroscopy and quantum chemistry. The stereochemistry of functionalized azoles is a challenging topic of theoretical research, as the correct interpretation of their chemical behavior and biological activity depends on understanding the factors that determine the stereochemical features and relative stability of their tautomers. NMR spectroscopy, in combination with quantum chemical calculations, is the most convenient and reliable approach to the evaluation of the stereochemical behavior of, in particular, nitrogen-containing heteroaromatic and heterocyclic compounds. Over the last decade, ¹⁵N NMR spectroscopy has become almost an express method for the determination of the structure of nitrogen-containing heterocycles. Full article

SrFe_12−xNb_xO₁₉ (x = 0.00–0.15) was here synthesized by a conventional solid-state reaction method. Thermogravimetry and differential scanning calorimetry curves revealed the sample reactions at four temperature ranges, and the optimal reaction stability was obtained at 1240 °C. A single-phase polycrystalline form of SrFe₁₂O₁₉ was obtained until the substitution reached 0.09, and the average crystallite size was found to be in the range of 44.21–60.02 nm. According to Fourier-transform infrared spectra, the formation of Fe–O bonds occurred at 69 and 450 cm⁻¹ in the M-type ferrite, while Raman spectra revealed that all the peaks in the sample corresponded to Raman vibration modes and M-type structures. Through the shift of the peaks, it is speculated that Nb⁵⁺ enters into the lattice. The hysteresis loops of the samples were measured by vibrating-sample magnetometry, and the calculated results demonstrated that the coercivity increased with increases in the doping amount (686.3 Oe). At the same time, the saturation magnetization remained at a large value (>72.49 emu/g), which has rarely been reported. Full article

Quantum chemical methods for the calculation of indirect NMR spin–spin coupling constants and chemical shifts are always in progress. They never stay the same due to permanently developing computational facilities, which open new perspectives and create new challenges every now and then. This review starts from the fundamentals of the nonrelativistic and relativistic theory of nuclear magnetic resonance parameters, and gradually moves towards the discussion of the most popular common and newly developed methodologies for quantum chemical modeling of NMR spectra. Full article