Spin Magnetic Effects Research Articles

Interface-Triggered Spin-Magnetic Effect in Rare Earth Intraparticle Heterostructured Nanoalloys for Boosting Hydrogen Evolution.

Rare earth (RE) elements are attractive for spin-magnetic modulation due to their unique 4 f electron configuration and strong orbital couplings. Alloying RE with conventional 3d transition-metal (TM) is promising for the fabrication of advanced spin catalysts yet remains much difficulties in preparation, which leads to the mysteries of spin-magnetic effect between RE and 3d TM on catalysis. Here we define a solid-phase synthetic protocol for creating RE-3d TM-noble metal integrated intraparticle heterostructured nanoalloys (IHAs) with distinct Gd and Co interface within the entire Rh framework, denoted as RhCo-RhGd IHAs. They exhibit interface-triggered antiferromagnetic interaction, which can induce electron redistribution and regulate spin polarization. Theoretical calculations further reveal that active sites around the heterointerface with weakened spin polarization optimize the adsorption and dissociation of H2O, thus promoting alkaline hydrogen evolution catalysis. The RhCo-RhGd IHAs show a small overpotential of 11.3 mV at 10 mA cm-2, as well as remarkable long-term stability, far superior to previously reported Rh-based catalysts.

Vacancy defect activation spin magnetic effect of Ni(OH)2 enhanced oxygen catalysis

The oxygen evolution reaction (OER) process involves the magnetic reversal of oxygen-containing intermediates, and the influence of defect structures on the magnetic behavior of catalysts might play a crucial role in this process. There is scarce research on the intrinsic relationship among defects, magnetism and catalysis. Herein, cation vacancy β-Ni(OH)2 nanosheets were successfully prepared through alkaline selective etching. To further analyze their spin-magnetic behavior, we found that the presence of defects caused the transformation of Ni(OH)2 from antiferromagnetic to ferromagnetic. Furthermore, to further elucidate their intrinsic spin-magnetic effects, it was observed that the initially antiferromagnetic β-Ni(OH)2 exhibited almost no spin-magnetic response upon the introduction of a magnetic field, with the overpotential almost unchanged. Conversely, introducing defect structures showed a noticeable spin-magnetic effect, reducing the overpotential by 20 mV at 20 mA cm−2. The combination of defects and magnetic fields provides new principles for developing high-performance catalysts and understanding catalytic mechanisms at the spin-electronic level.

Spin-Magnetic Effect of d-π Conjugation Polymer Enhanced O-H Cleavage in Water Oxidation.

A deep understanding of the mechanism for the spin-magnetic effect on O-H cleavage is crucial for the development of new catalysts for water oxidation. Herein, we designed and synthesized the crystalline Fe-DABDT and Co-DABDT (DABDT = 2,5-diaminobenzene-1,4-dithiol) and optimized an effective magnetic moment to explore the role of the spin-magnetic effect in the regulation of water oxidation activity. It can be found that the OER activity of the catalyst is positively correlated with its effective magnetic moment. Under the external magnetic field, Fe-DABDT with more spin single electrons has a stronger spin-magnetic response to water oxidation than Fe/Co-DABDT and Co-DABDT. The increase in OER current of Fe-DABDT is nearly 2 times higher than that of Co-DABDT. Experimental and density functional theory studies show that magnetized Fe sites could realize nucleophilic reaction, accelerate the polarization of electron spin states, and promote the polar decomposition of O-H and the formation of the O-O bond. This study provides mechanistic insight into the spin-magnetic effect of oxygen evolution reaction and further understanding of the spin origin of catalytic activity, which is expected to improve the energy efficiency of hydrogen production.

Revealing Spin Magnetic Effect of Iron-Group Layered Double Hydroxides with Enhanced Oxygen Catalysis

The oxygen evolution reaction (OER) is the bottleneck limiting the reaction process of water splitting. The OER process involves the recombination of oxygen from diamagnetic singlet state OH or H2O to paramagnetic triplet state O2. The spin conservation for oxygenated intermediates must play an important role in the OER. However, the dynamic mechanism of magnetic field-induced spin polarization is still in its infancy. Herein, based on the spin-coupling interaction of iron group elements, three typical iron group layered double hydroxides (LDHs) were constructed to study the relationship among magnetic field, spin polarization, and OER activity. Combining experimental and theoretical studies, we revealed the spin-magnetic effect of iron group LDHs for enhancing the OER process. There is a positive correlation between the saturation magnetization and OER performance of iron group LDHs under different magnetic fields. The NiCoFe-LDHs (NCFL) endows the strongest OER activity (η10 = 230 mV) and saturation magnetization (Ms = 44 emu mg–1) compared with that of CoFe-LDHs (CFL, η10 = 372 mV, Ms = 21 emu mg–1) and NiFe-LDHs (NFL, η10 = 246 mV, Ms = 29 emu mg–1). The density functional theory calculations show that the Fe sites of NCFL endow a stronger spin-coupling interaction with OH, and Raman spectroscopy further proves the promotion for the formation of the O–O bond of NCFL. Applying an external magnetic field, due to the spin magnetic effect of iron group LDHs, the enhancement amplitude of OER activity is also positively correlated with the magnetism of the catalyst. NCFL has the strongest spin magnetic effect about −34.8 mV T–1 compared with NFL (−27.0 mV T–1) and CFL (−16.7 mV T–1). The overpotential of NCFL is only 206 mV under the condition of 700 mT magnetic field. In conclusion, we demonstrate the mechanism of underlying influence of the spin magnetic effect on the OER performance and provide insights into the relationship between catalysts and oxygenated intermediates. These insights would help to understand and design catalysts at the spintronic level.

Controversial Issues of Hydrocarbon Field Formation and the Role of Geomagnetic Fields

This review paper presents controversial issues on the formation of hydrocarbon deposits. We look into the geological contradictions of the abiogenic and biogenic theories of petroleum origin, indicating the connection between hydrocarbon deposits and disjunctive dislocations, as well as present disputes about the geological period over which hydrocarbon deposits have been formed. We further overviewed the radical chain mechanism of hydrocarbon generation from organic matter as proposed by Prof. Nesterov. It is noted that the petroleum generation process in reservoir conditions occurs almost instantly in the presence of discrete geomagnetic fields and does not require a long geological time. This is explained by spin magnetic effects (spin catalysis, magnetic isotope properties). We briefly highlight the effect of magnetic fields on chemical reactions involving organic compounds and the use of magnetic fields to enhance oil recovery. We also present the leading causes of discrete magnetic fields in the sedimentary cover: Earth’s geomagnetic reversals, generation of ferromagnetic minerals in oil deposits, electromechanical effects of rock friction near faults, and intermixing of reservoir waters with different mineralization (spontaneous ion polarization). Based on the material reported, we conclude that the radical chain mechanism of petroleum generation processes explains some contradictions of the abiogenic and biogenic theories of petroleum origin. Elaborating this research area has excellent prospects for developing new criteria for hydrocarbon prospecting and devising innovative methods to enhance the oil recovery for shale oil production.

Photoconductivity of Polyalkanetherimide Composite Films Containing Rubrene Microcrystals and Magnetic Nanoparticles

The effect a weak magnetic field in the hyperfine (HFI) range (Н < 1 kG) has on the yield of luminescence, excitonic photoconductivity (EPC) (spin magnetic effects, or SMEs), and the drop in SMEs upon adding magnetic nanoparticles (MNP) with lowered Curie points (40–60°C) (the SME decrement) is determined for composite polymeric films containing rubrene microcrystals at room temperature. Investigation of the photocurrent kinetics in real time scales shows that in addition to the non-inertial EPC (with times shorter than 1 s), there is a weaker inertial (time, 23.5 min) secondary thermostimulated current (TSC) caused by the capture of photo-generated current carriers by deep centers with subsequent thermal release, and lacking sensitivity to the magnetic field. It is determined that the centers of capture are MNPs with considerable affinity toward electrons. The formation of a supply of long-lived MNP−s (captured carriers) results in a marked decrement of SMEs on the EPC. A peak of MNP–s (nanoparticles with captured electrons), formed upon both the dark electron transition and the capture of photoelectrons, is observed at Н = 2830–2900 G in the spectra of the ferromagnetic resonance for the composite films. It is concluded that such a notable decrement of SMEs on the EPC is associated with the substantial change in MNP magnetic characteristics upon the capture of electrons, as was observed earlier for interaction with excitons (an indirect mechanism of interaction).

Organic superconductors in the Pauli paramagnetic limit region

The low-dimensionality of the organic superconductors leads the pronounced anisotropy in the upper critical field. In the vicinity of the field direction parallel to the superconducting plane, the critical field shoots out due to the suppression of the orbital pair-breaking effect and is determined by the spin magnetic effect. The organic superconductors are suitable for the study of the high field state related to the spin effect under aligned field, since they are of high crystalline quality. The reported experimental results covering the behavior at low temperature are reviewed first and the breakthrough of the BCS Pauli paramagnetic limit is argued. The in-plane anisotropy of the upper critical field is also touched upon.

Resonance interaction between shallow electron states of donor and acceptor impurities subjected to an extremely strong external magnetic field

The two-level theoretical model has been introduced for the investigation of optical transitions of electrons between shallow impurity states close to opposite edges of the forbidden gap under the influence of resonant laser radiation in doped semiconductors of GaAs and InSb type subjected to a strong magnetic field. The initial (non-interacting) form of a single electron energy spectrum and the mode of its wavefunctions have been derived from modified application of an adiabatic method, with the acceptance of a scalar effective mass approximation for both condition and valence bands. In the case of a single electron resonance interaction with an isolated pair of contrarily charged impurity centres the specific features of high-frequency Stark shifts in strong magnetic fields have been investigated, and analytical expressions have been obtained reflecting the dependence of shift magnitudes on magnetic field intensities. A separate consideration of spin magnetic effects has been conducted. In a bulk semiconductor non-homogeneous high-frequency shift of ground state binding energies has been investigated. The mean average energy values of high-frequency shift and Coulomb interaction between impurities have been determined as functions depending on the impurities' concentration and magnetic field intensity.

Nonuniform superconductivity due to the orbital magnetic effect in a d-wave superconductor in a magnetic field.

A type-II superconductor with d-wave pairing interactions with anisotropy due to the crystal lattice is studied. A kind of nonuniform superconductivity due to the orbital magnetic effect with a spatially oscillating order parameter is found to occur under appropriate conditions on the coupling constants and the direction of the magnetic field. It is found that the state depends on the direction of the magnetic field strongly. The spin magnetic effect on this nonuniform superconducting state is also examined. The relevance to the recent experimental result in heavy fermion ${\mathrm{UPd}}_{2}$${\mathrm{Al}}_{3}$ system is discussed. \textcopyright{} 1996 The American Physical Society.

III International Symposium on Spin Magnetic effects in chemistry and related phenomena

III International Symposium on Spin Magnetic effects in chemistry and related phenomena

Spin Magnetic Effect on the Polarization of the Electron-Atom Impact Radiation

A new mechanism is proposed to explain the discrepancies between the measured and the expected polarization of the electron-atom impact radiation at threshold energy. The idea is the following: At threshold scattering, the spin of the scattered electron interacts magnetically with the orbital motion of the atomic electrons. The component of this magnetic interaction along the quantization axis, which is perpendicular to the incident electron direction, will split the magnetic sublevels of the atomic excited states. This splitting will cause the coherent interference of the radiation, which originates from two degenerate upper levels and ends on a single lower level, to become ineffective. The polarization of the radiation is thereby affected and in fact decreases. The expected polarization $P$ is modified by a depolarization factor $f={(1+{〈{\ensuremath{\omega}}^{2}〉}_{\mathrm{av}}{\ensuremath{\tau}}^{2})}^{\ensuremath{-}1}$, where $\ensuremath{\omega}$ is the frequency splitting of the excited state, and $\ensuremath{\tau}$ is the lifetime of the transition from the excited upper state to a lower state. By using a simple product wave function for the state, the $\ensuremath{\omega}$ and hence the $P$ for various singlet-singlet transitions and triplet-triplet transitions have been calculated for the helium atom. In general, when the principal quantum number $n$ of the excited state, where the radiation originates, increases, $f$ also increases and approaches unity. Consequently, $P$ increases and approaches the expected value. For example, $P$ for the $3^{1}P\ensuremath{\rightarrow}2^{1}S$ (5016 \AA{}) line turns out to be 1.2%, whereas for the $4^{1}D\ensuremath{\rightarrow}2^{1}P$ (4922 \AA{}) line it turns out to be 50%. The expected values are 100% and 60%, respectively. In the case of triplet-triplet transitions, the spin-spin interaction between the scattered electron and the atomic electrons is also included.