Ferromagnetic Spin Coupling Research Articles

Tuning structure, stability and magnetism in vanadium doped zinc sulfide for spintronic applications: Insights from first-principles and Monte Carlo approaches

This work utilizes a multi-scale computational approach combining first-principles density functional theory (DFT) and Monte Carlo statistical simulations to provide fundamental insights into the impacts of vanadium (V) doping on the structural, electronic, magnetic, and thermodynamic properties of wurtzite zinc sulfide (ZnS). 2 × 2 × 2 ZnS supercells with controlled V doping concentrations from 12.5%–25% substituting zinc sites were constructed. The introduction of V dopants induces systematic expansions in lattice parameters and cell volume, attributed to the larger ionic radius of V2+ than Zn2+, while the average compressibility shows minimal variation. However, V incorporation is found to soften ZnS by over 15% at higher dopant contents, increasing compliance and anisotropy. Stable ferromagnetic spin couplings emerge, mediated by host carriers without precipitating V secondary phases. The band structure develops half-metallic electronic properties with the lifting of spin degeneracy and preferential spin-up band metallicity induced by V-3d and S-3p hybridization effects. This results in 100% spin polarization at the Fermi level. Monte Carlo simulations based on a tight-binding Hamiltonian constructed from maximally localized Wannier functions to accurately calculate the exchange interactions between V spins successfully reproduce the magnetic phase transition behavior. The results confirm high Curie temperatures exceeding 300 K at 25% V, attributable to the significant strengthening of short-range ferromagnetic couplings over antiferromagnetic interactions. The integrated computational approach provides fundamental insights into the microscopic origin of carrier-mediated ferromagnetism in V-doped wurtzite ZnS dilute magnetic semiconductors. The systematic first-principles calculations and statistical mechanics modeling establish clear structure–property relationships linking V doping configurations and concentrations to tuned mechanical response, enhanced stability, electronic structure modifications, spin polarization, and magnetic ordering temperatures in ZnS. The results present design pathways and predictive capabilities to guide experimental efforts toward emerging high-performance magnetic materials for spintronic technologies.

Single-hole spectra of Kitaev spin liquids: from dynamical Nagaoka ferromagnetism to spin-hole fractionalization

The dynamical response of a quantum spin liquid upon injecting a hole is a pertinent open question. In experiments, the hole spectral function, measured momentum-resolved in angle-resolved photoemission spectroscopy (ARPES) or locally in scanning tunneling microscopy (STM), can be used to identify spin liquid materials. In this study, we employ tensor network methods to simulate the time evolution of a single hole doped into the Kitaev spin-liquid ground state. Focusing on the gapped spin liquid phase, we reveal two fundamentally different scenarios. For ferromagnetic spin couplings, the spin liquid is highly susceptible to hole doping: a Nagaoka ferromagnet forms dynamically around the doped hole, even at weak coupling. By contrast, in the case of antiferromagnetic spin couplings, the hole spectrum demonstrates an intricate interplay between charge, spin, and flux degrees of freedom, best described by a parton mean-field ansatz of fractionalized holons and spinons. Moreover, we find a good agreement of our numerical results to the analytically solvable case of slow holes. Our results demonstrate that dynamical hole spectral functions provide rich information on the structure of fractionalized quantum spin liquids.

Metal vs Ligand Oxidation: Coexistence of Both Metal-Centered and Ligand-Centered Oxidized Species.

A series of two-electron-oxidized cobalt porphyrin dimers have been synthesized upon controlled oxidations using halogens. Rather unexpectedly, X-ray structures of two of these complexes contain two structurally different low-spin molecules in the same asymmetric unit of their unit cells: one is the metal-centered oxidized diamagnetic entity of the type CoIII(por), while the other one is the ligand-centered oxidized paramagnetic entity of the type CoII(por•+). Spectroscopic, magnetic, and DFT investigations confirmed the coexistence of the two very different electronic structures both in the solid and solution phases and also revealed a ferromagnetic spin coupling between Co(II) and porphyrin π-cation radicals and a weak antiferromagnetic coupling between the π-cation radicals of two macrocycles via the bridge in the paramagnetic complex.

Rational Design of an Air-Stable, High-Spin Diradical with Diazapyrene.

Stable carbon-based polyradicals exhibiting strong spin-spin coupling and slow depolarization processes are particularly attractive functional materials. A new molecular motif synthesized by a convenient method that allows the integration of stable, high-spin radicals to (hetero)aromatic polycycles has been developed, as illustrated by a non-Kekulé diradical showing a triplet ground state with long persistency (τ1/2 ≈31 h) in air. Compared to the widely used 1,3-phenylene, the newly designed (diaza)pyrene-4,10-diyl moiety is for the first time demonstrated to confer ferromagnetic (FM) spin coupling, allowing delocalized non-disjoint SOMOs. With the X-ray crystallography unambiguously proving the diradical structure, the triplet ground state was thoroughly characterized. A large ΔES-T of 1.1 kcal/mol, proving the strong FM coupling effect, was revealed consistently by superconducting quantum interference device (SQUID) measurements and variable-temperature electron paramagnetic resonance (EPR) spectroscopy, while the zero-field splitting and triplet nutation characters were examined by continuous-wave and pulsed EPR spectroscopy. A millisecond spin-lattice relaxation time was also detected. The current study not only offers a new molecular motif enabling FM coupling between carbon-based spins, but more importantly presents a general method for installing stable polyradicals into functional π-systems.

Rational Design of an Air‐Stable, High‐Spin Diradical with Diazapyrene

AbstractStable carbon‐based polyradicals exhibiting strong spin‐spin coupling and slow depolarization processes are particularly attractive functional materials. A new molecular motif synthesized by a convenient method that allows the integration of stable, high‐spin radicals to (hetero)aromatic polycycles has been developed, as illustrated by a non‐Kekulé diradical showing a triplet ground state with long persistency (τ1/2≈31 h) in air. Compared to the widely used 1,3‐phenylene, the newly designed (diaza)pyrene‐4,10‐diyl moiety is for the first time demonstrated to confer ferromagnetic (FM) spin coupling, allowing delocalized non‐disjoint SOMOs. With the X‐ray crystallography unambiguously proving the diradical structure, the triplet ground state was thoroughly characterized. A large ΔES‐T of 1.1 kcal/mol, proving the strong FM coupling effect, was revealed consistently by superconducting quantum interference device (SQUID) measurements and variable‐temperature electron paramagnetic resonance (EPR) spectroscopy, while the zero‐field splitting and triplet nutation characters were examined by continuous‐wave and pulsed EPR spectroscopy. A millisecond spin‐lattice relaxation time was also detected. The current study not only offers a new molecular motif enabling FM coupling between carbon‐based spins, but more importantly presents a general method for installing stable polyradicals into functional π‐systems.

Weak ferromagnetism at 48.5 K in rubidium-intercalated biphenyl

Aromatic hydrocarbon molecules with π-conjugated structure have great potential for the search of exotic states such as high temperature superconductivity and novel quantum magnetism. In this work, we found that high temperature weak ferromagnetism can be achieved by intercalating rubidium into the shortest poly(para-phenylene) molecule—biphenyl. Both dc and ac magnetic susceptibility measurements showed that the synthesized material exhibits a typical antiferromagnetic transition at 48.5 K, accompanying a ferromagnetic character in the magnetically ordered region. Combining theoretical calculations and Raman spectroscopic studies, it was found that the mole ratio between rubidium and biphenyl is 1:1, and the molecular magnetic moments are formed by transferring the Rb-5s electrons to the C-2p orbitals. The weak ferromagnetism is produced by intralayer spin-canted antiferromagnetic and interlayer ferromagnetic spin couplings. Our finding enriches the physicochemical functionality of biphenyl and opens a window for the search of π-electron organic magnets in poly(para-phenylene) molecules.

Electron-Coupled Proton Transfer Governed Magnetic Spin Couplings and Switching in Defect Nano Silicon Carbide

The formation mechanism, defect characterization, and potential applications of the Si vacancy (VSi) with internal H atoms in the silicon carbide (SiC) materials have been widely investigated. However, the inherent electronic properties and related phenomena induced by internal H dynamics in VSi, especially the C-radical spin interaction dynamics, are still poorly understood in such nano SiC. In this work, using the density functional calculations, we explore the magnetic coupling characteristics and dynamic behaviors induced by H-motion in nano SiC with four different types of H-doped VSi defect centers, (VSi + H)−, (VSi + H)+, (VSi + 2H), and NVH [i.e., (NCVSi + H)0 in which one of C-radical sites in VSi is replaced by N]. Our results reveal their unique ferromagnetic (FM) or antiferromagnetic (AFM) spin coupling characteristics and H-motion-induced interconversion. In general, the internal H-motion goes through the electron-coupled proton transfer (ECPT) in a C–H···C unit which has great impact on molecular orbitals, spin densities, and thus spin couplings among the C-radicals, allowing the VSi center to undergo magnetic switching between FM and AFM coupling. Interestingly, as in the (VSi + H)− center, such ECPT can further drive the excess electron delocalized on three C-radicals to gather at the ECPT unit, forming a three-center-four-electron (3c–4e) [C···H···C]− covalent H-bond with the switching of magnetic coupling. This work provides the dynamics insights into the spin coupling characteristics and its regulation by internal H-motion and multiple radical characters of such defect materials and the formation of a 3c–4e H-bond assisted by excess electron, and also provides inspired information for the design of inorganic magnetic materials and logic devices which can be controlled by interior doping and dopant dynamics.

Nuclear and magnetic spin structure of the antiferromagnetic triangular lattice compound LiCrTe2 investigated by mu ^+SR, neutron and X-ray diffraction

Two-dimensional (2D) triangular lattice antiferromagnets (2D-TLA) often manifest intriguing physical and technological properties, due to the strong interplay between lattice geometry and electronic properties. The recently synthesized 2-dimensional transition metal dichalcogenide LiCrTe_2, being a 2D-TLA, enriched the range of materials which can present such properties. In this work, muon spin rotation (mu ^+SR) and neutron powder diffraction (NPD) have been utilized to reveal the true magnetic nature and ground state of LiCrTe_2. From high-resolution NPD the magnetic spin order at base-temperature is not, as previously suggested, helical, but rather collinear antiferromagnetic (AFM) with ferromagnetic (FM) spin coupling within the ab-plane and AFM coupling along the c-axis. The value if the ordered magnetic Cr moment is established as mu _{textrm{Cr}}= 2.36~mu _{textrm{B}}. From detailed mu ^+SR measurements we observe an AFM ordering temperature T_{textrm{N}}approx 125 K. This value is remarkably higher than the one previously reported by magnetic bulk measurements. From mu ^+SR we are able to extract the magnetic order parameter, whose critical exponent allows us to categorize LiCrTe_2 in the 3D Heisenberg AFM universality class. Finally, by combining our magnetic studies with high-resolution synchrotron X-ray diffraction (XRD), we find a clear coupling between the nuclear and magnetic spin lattices. This suggests the possibility for a strong magnon–phonon coupling, similar to what has been previously observed in the closely related compound LiCrO_2.

Effects of Thermal Annealing on Optical and Microscopic Ferromagnetic Properties in InZnP:Ag Nano-Rods.

InZnP:Ag nano-rods fabricated by the ion milling method were thermally annealed in the 250~350 °C temperature range and investigated the optimum thermal annealing conditions to further understand the mutual correlation between the optical properties and the microscopic magnetic properties. The formation of InZnP:Ag nano-rods was determined from transmission electron microscopy (TEM), total reflectivity and Raman scattering analyses. The downward shifts of peak position for LO and TO modes in the Raman spectrum are indicative of the production of Ag ion-induced strain during the annealing process of the InZnP:Ag nano-rod samples. The appearance of two emission peaks of both (A0 X) and (e, Ag) in the PL spectrum indicated that acceptor states by Ag diffusion are visible due to the effective incorporation of Ag-creating acceptor states. The binding energy between the acceptor and the exciton measured as a function of temperature was found to be 21.2 meV for the sample annealed at 300 °C. The noticeable MFM image contrast and the clear change in the MFM phase with the scanning distance indicate the formation of the ferromagnetic spin coupling interaction on the surface of InZnP:Ag nano-rods by Ag diffusion. This study suggests that the InZnP:Ag nano-rods should be a potential candidate for the application of spintronic devices.

Endohedral σ-Diradical Nitrogen-Vacancy Diamond Nanoclusters with a Confined Magnetic Space and Strong Electronic Spin Couplings.

The electronic properties and their modulations for the nitrogen-vacancy (NV) centers in various nanoscale diamonds are of profound current interest because of their potential applications. However, although the NV centers as chromophores in diamond are the most widely studied, surprisingly, little is known about their magnetic spin coupling properties up to now. Here, we for the first time show, using the spin-polarized DFT calculations, that the NV centers can act as unique endohedral σ-diradical magnets in diamond nanoclusters and exhibit quite strong ferromagnetic (FM) or antiferromagnetic (AFM) spin coupling characteristics due to their unique endotetrahedral structures with favorable radical-radical contacts. Although the neutral NV center (NV0) in its doublet ground state exhibits quite strong AFM spin coupling among three radical C-sites (i.e., an AFM triradical center), interestingly, excess electron injection can convert it to a FM diradical magnet (i.e., the triplet ground state NV-) with almost unchanged J-coupling magnitude, and the J-coupling of the nanocluster can be noticeably enhanced by F-termination of the surface due to triradical spin delocalization mediated by excess electron. However, interior modification (one C in the endotetrahedron core is substituted by N or B or is hydrogenated) can assign the nanocluster perfect AFM diradical character. The spin coupling strength presents a quasilinear correlation with the distance between the two C radicals in the NV core for the same size of the clusters and a high linear correlation with the energy difference between two singly occupied molecular orbitals. Clearly, the FM and AFM couplings as well as their switching behavior in such NV defect diamond nanoclusters featuring the endohedral σ-diradicals are a novel type of promising magnetic material motifs. These findings open up promising spintronic application prospects of the NV diamonds and provide helpful information for the design of inorganic magnetic materials and logic devices.

Salts of vanadyl phthalocyanine {VIVO(Pc•3−)}− anions with decamethylmetallocenium cations (Cp*2M+, M = CrIII and CoIII). Ferromagnetic coupling in the [(Cp*2Cr+){VIVO(Pc•3−)}−]2 assemblies

Vanadyl phthalocyanine {VIVO(Pc2−)}0 was reduced by decamethylchromocene or decamethylcobaltocene (Cp*2MII), and the crystals of the complexes were precipitated by n-hexane. Reduction of this phthalocyanine is centered on the macrocycle providing the formation of the {VIVO(Pc•3−)}− anions containing two paramagnetic VIV and Pc•3− centers with an S = 1/2 spin state. These paramagnetic anions coexist in (Cp*2Cr+){VIVO(Pc•3−)}−·3C6H4Cl2 (1) with the high-spin (S = 3/2) Cp*2Cr+ counter cations. Nearly isolated assemblies in which two Cp*2Cr+ cations are sandwiched between two {VIVO(Pc•3−)}− anions are formed in 1. Effective magnetic moment of 1 of 4.57 μB at 300 K corresponds to the contribution of noninteracting VIV, Pc•3− and CrIII spins. Weiss temperature of +4 K indicates weak ferromagnetic coupling of spins. Effective magnetic moment of 1 increases upon cooling up to 4.78 μB at 8 K and then drastically falls down. Such magnetic behavior is described well by ferromagnetic coupling between the VIV and Pc•3− spins with J1 = + 4.75 cm−1 and weaker ferromagnetic interactions between Pc•3− and CrIII spins through the Cp* ligand with J2 = +1.08 cm−1. Weak antiferromagnetic coupling with J3 = −0.76 cm−1 is also present between the CrIII spins. Complexes (Cp*2Co+){VIVO(Pc•3−)}−·1.5C6H4Cl2 (2) and (Cp*2Co+) {VIVO(Pc•3−)}−·C6H4Cl2 (3) with the diamagnetic Cp*2Co+ counter cations (S = 0) were also obtained allowing to study their crystal structures and optical properties.

Magnetic polaronic and bipolaronic excitons in Mn(II) doped (TDMP)PbBr4 and their high emission

If we introduce transition metal ions with spins into an organic-inorganic halide perovskite compounds, interesting spin dependent optical properties may be seen in this system. This paper reports an organic-inorganic hybrid manganese ion doped lead halide crystal incorporated by TDMP (trans-2,5-dimethylpiperazinium), it gives not only the STE1 (polaronic exciton), usually brought up by the enhanced electron-phonon coupling in the amine incorporated compound, but also give a novel bipolaronic exciton (STE2) for the paired charge state formation due to the incorporation of bi-amine cationic molecules, a excitation by the polaronic molecule due to enhanced electron-phonon coupling and neighboring correlation out of the Mn ion ferromagnetic spin coupling in the lattice at slightly high doping. Such magnetic bipolaron state could often be accompanied by several multiphonon Raman modes and ferromagnetism. It is even interesting that this state can give super-high red emission with PLQY at ~92.5% at room temperature. Moreover, the emission color and intensity could also be modulated by the Mn doping concentration, temperature, and laser excitation power. The low doping products can give green emission out of single Mn d-d transition at very low temperature or high laser excitation power. The intermediately doped products can give white emission out of STE1 and STE2. The highly doping products give red emission out of STE2 (bipolaron states) at room temperature or low laser power. These interesting phenomena reflected the microscopic interactions between spins, carriers and phonons in the products, which can be found applications in the future fields of photonics and spintronics.

π-electron weak ferromagnetism in potassium-intercalated 9-phenylanthracene

Intercalation of alkali metal is an effective way to tune the physicochemical property of polyaromatic hydrocarbons. Herein, we show for the first time that the weak ferromagnetism with a Curie temperature of 5.2 K can be realized in an all-carbon π-electron compound – potassium-intercalated 9-phenylanthracene. The magnetic measurements reveal that there exists an antiferromagnetic transition around 35 K before transition to the weak ferromagnetic phase. An in-depth theoretical investigation indicates that the weak ferromagnetism is produced by the intramolecular ferromagnetic and intermolecular antiferromagnetic spin couplings in the crystal unit cell. Our finding enriches the physical functionality of anthracene derivatives and adds a new member of organic magnetic materials.

Polariton condensate trapping by parametric pair scattering

Spatially confined, trapped polariton condensates have been shown to exhibit strong stochastic on-site spin polarization and in longer polariton condensate chains, distance controlled ferromagnetic and antiferromagnetic spin couplings. Until now, little is known, on how such polariton condensates spatially separated from their exciton reservoirs are trapped and formed. Here, we investigate the properties and formation dynamics of two main families of polariton condensates, those overlapping with the pump reservoir and those in confined geometries, under pulsed nonresonant excitation. The observed reduction in polariton condensation threshold and energy blueshift in trapped case is attributed to exciton reservoir-condensate spatial separation, whereas time-resolved photoluminescence measurements, reveal distinct relaxation and condensate formation dynamics with pair parametric scattering process being the dominant relaxation mechanism in trapped geometry.

Room-temperature ferromagnetism in boron-doped oxides: a combined first-principle and experimental study

ABSTRACTThe ferromagnetic properties of boron-doped oxides, namely ZnO, MgO, CdO and TiO2 have been studied using first-principle calculations based on density functional theory. A boron atom, when doped at an anion site, generates a magnetic moment per dopant atom ranging from ∼1 µB in TiO2 to ∼3 µB in ZnO. The source of magnetism in the boron-doped oxides is the 2p-orbital electrons of the dopant atom plus a small contribution coming from the oxygen atoms surrounding the dopant. A spin–spin interaction study reveals that the doping of B at O sites favours ferromagnetic spin coupling in ZnO, MgO, CdO and TiO2. Boron-doped samples have been prepared by ion-beam irradiation with a 10 keV B+ beam implanting on sample pallets. Magnetic measurements have been carried out for B+-ion-implanted oxide samples using a SQUID magnetometer. A stable room-temperature ferromagnetic ordering is observed in boron-ion-irradiated ZnO, MgO, CdO and TiO2 samples.

Mean field theory and Monte Carlo simulation of phase transitions and magnetic properties of a tridimensional Fe7S8 compound

The structural, electronic and magnetic properties of Fe7S8 material have been studied within the framework of the ab initio calculations, the mean field approximation (MFA) and Monte Carlo simulation (MCS). Our study shows that two forms of the iron atoms, Fe2+ with spin S = 2, and Fe3+ with spin = 5/2 are the most probable configurations. A mixed Ising model with ferromagnetic spin coupling between Fe2+ and Fe3+ ions and between Fe3+ and Fe3+ ions, and with antiferromagnetic spin coupling between Fe2+ ions of adjacent layers has been used to study the magnetic properties of this compound. We demonstrated that the magnetic phase transition can be either of the first or of the second order, depending on the value of the exchange interaction and crystal field. The presence of vacancies in every second iron layer leads to incomplete cancellation of magnetic moments, hence to the emergence of the ferrimagnetism. Anomalies in the magnetization behavior have been found and compared with the experimental results.

Effect of Compensation on Low-Temperature Spin Ordering in Ge:As Semiconductor Near the Insulator–Metal Phase Transition

An electron-spin resonance technique has been used to examine the influence exerted by the degree of compensation on spin effects in a set of nonmagnetic Ge:As semiconductor samples in the vicinity of the insulator–metal phase transition at temperatures 2 K ≤ T ≤ 80 K. It was found that the behavior of the paramagnetic susceptibility, specific to the Pauli paramagnetism and manifested in the spin density resonance, is drawn deep into the insulator state and is observed up to rather large degrees of compensation K ≈ 0.7 at temperature 20 K ≥ T ≥ 5–10 K. Outside this temperature range, both the quantities rapidly grow with increasing compensation and their behavior approaches the Curie law characteristic of the strong insulator state. The reason for this behavior is that the degeneracy is lifted at high temperatures and, at low temperatures, electron states are localized at the Fermi level as a result of the Coulomb blockade by compensating acceptors of the most closely lying donor states and the resulting formation of a narrow Coulomb band in the metallized impurity band. At temperature T ≥ 5–10 K, the gap is blurred by thermal excitations and has no effect on the manifestation of the Pauli paramagnetism. The behavior of the line width of the electron-spin resonance is determined by the scattering on quasi-stationary electric dipoles created by the Coulomb blockade at low temperatures and by the scattering on phonons at high temperatures. The behavior of the g-factor is qualitatively correlated with the specific features of the paramagnetic susceptibility and spin density: with decreasing temperature it weakly grows in the range of the Pauli paramagnetism and then rapidly increases in the range in which the Coulomb blockade is manifested and a transition occurs to the Curie law. By an analogy with ferromagnetic materials in which such a fast increase in the g-factor is observed, the possibility of a compensation caused ferromagnetic coupling of spins localized on donors. The microscopic model of such a coupling is discussed.

Electronic and Magnetic Properties of Iron Clusters Encapsulated in Carbon Nanotubes

We have made theoretical study of the electronic and magnetic properties of iron clusters encapsulated in carbon nanotubes using density functional theory. We have considered cluster encapsulated inside finite pieces of single wall zigzag nanotubes of indices (11,0) and (10,0). Finite zigzag nanotubes have a peculiar magnetic structure, the ground state is an antiferromagnetic spin singlet S=0. The local spin polarization oscillates along the direction of the nanotubes axis and is small, except at the two ends of the edges of the nanotubes. We have studied the encapsulation of iron atoms and small Fen clusters n = 2,4,8 in a short (10,0) tube. By the constraints imposed by the cylindrical geometry of a narrow nanotubes, we have considered the encapsulation of an isomer of F12 with an elongated structure. We have also considered the encapsulation of the lowest energy, icosahedral structure of Fe12. The free elongated Fe12 isomer presented a strong ferromagnetic spin coupling giving rise to a large magnetic moment. The distortion in the density of state of the iron cluster is much smaller preserving the strong ferromagnetic character. There is some p-d hybridization between the nanotubes and the cluster states, mainly around the Fermilevel. The loweswt unoccupied molecular orbital of the pristine zigzag nanotubes becomes partially occupied due to charge transfer from the cluster to the nanotubes. We have analysed the interplay between the singular magnetic properties of the finite zigzag nanotubes and the large magnetization of the encapsulated iron clusters. The calculations indicated that the magnetism is confined within the iron aggregates, with small reduction of the magnetic moment per atom with respect to the free iron clusters. The magnetic moment per atom result enhanced with respect to those of bulk iron, due to the reduced coordination of the metal atoms. The obtained results were found in good agreement with previously obtained results.

A very simple proof of the LSI for high temperature spin systems

We present a very simple proof that the O(n) model satisfies a uniform logarithmic Sobolev inequality (LSI) if the difference between the largest and the smallest eigenvalue of the coupling matrix is less than n. This condition applies in particular to the SK spin glass model at inverse temperature β<1/4. It is the first result of rapid relaxation for the SK model and requires significant cancellations between the ferromagnetic and anti-ferromagnetic spin couplings that cannot be obtained by existing methods to prove Log-Sobolev inequalities. The proof also applies to more general bounded and unbounded spin systems. It uses a single step of zero range renormalisation and Bakry–Emery theory for the renormalised measure.

Dielectron Clathrate Hydrates with Unique Superexchange Spin Couplings

Clathrate hydrates have exhibited prospective applications not only in energy and environmental fields but also in icy magnetic materials because of the possibility of inclusion of radical species and their unique structures. In particular, the existence of dielectron clathrate hydrates has been experimentally reported. However, their structures and electronic or spintronic properties have not been explored yet. Here, we investigate four kinds of dielectron clathrate hydrates ((H2O)n2–, n = 36, 44, 48, and 52) and their spintronic properties using the density functional theory method and find that all dielectron hydrates feature stable bipolarons in icy surroundings with internal or H-bonding network permeating state electron distributions. The dielectron presents significant antiferromagnetic or ferromagnetic spin couplings through a novel electron-permeating H-bonding network superexchange mechanism. This work opens up the possibility of exploring novel icy crystal magnetic materials based on the clathr...