Value Of Magnetic Moment Research Articles

Structural, optoelectronic, and magnetic properties of Q‑carbon studied by hybrid density functional theory ab initio calculations and experiment

This work presents a theoretical study of the structural, optoelectronic, and magnetic properties of Q‑carbon, utilizing hybrid functionals within density functional theory (DFT) ab initio calculations. Moreover, experiments were conducted to measure structural parameters, dielectric functions, and magnetic properties, using various techniques. From the DFT simulations, structural, electronic, and optical properties have been simulated. The band gap energy was calculated using a hybrid approach, which combine HSE functional with different values of exact Hartree-Fock (HF) exchange (α). We propose a theoretical investigation of cubic and quasi-cubic forms of Q‑carbon. Our findings indicate that a non-cubic Q‑carbon cell is energetically more stable and possesses higher cell mass density and bulk modulus compared to a cubic cell. Calculations indicated that Q‑carbon exhibits semiconductor behavior; an indirect band gap of 3.10 eV and a direct band gap of about 3.4 eV was obtained for α = 0.44, in good agreement with experimental values. The density of states analysis allowed us to identify the p orbital of sp2 hybridized atoms as being prevalent on the top of the valence band and in the lowest energy conduction band states. Magnetic moment values of 0.37 μB and 0.41μB was found in two sp2 bonded C atoms, in accordance with the experimental observation. Several optical properties were calculated. The theoretical findings are compatible with the experimental results shown here and available in the literature, with excellent agreement found between the calculated optical band gap and that obtained from absorption measurements.

Pioneering computational insights into the structural, magnetic, and thermoelectric properties of A3XN (A=Co, Fe; X=Cu, Zn) anti-perovskites for advanced material applications

This study pioneers the utilization of computer-controlled simulations to elucidate the structural, elastic, electronic, and thermoelectric properties of A3XN anti-perovskites (A = Co, Fe; X = Cu, Zn). Starting with the development of a detailed structural model, structural optimization calculations identify the stable Pm-3m cubic phase, aligning with experimental findings. Also, these optimizations indicate the ferromagnetic phase stability of A3XN anti-perovskites, further supported by positive Curie-Weiss constants of 60 K, 80 K, and 100 K for Co₃CuN, Co₃ZnN, and Fe₃CuN, respectively. The spin-dependent electronic properties, including band structure and density of states, are explored using multiple exchange-correlation (XC) functionals—GGA, GGA + U, and GGA + mBJ. The results uphold the metallic nature of the materials, accompanied by significant spin magnetic moments. Specifically, the calculated values of magnetic moments for Co3CuN, Co3ZnN, and Fe3CuN are 5.08 μB, 3.70 μB, and 7.61 μB, respectively. Furthermore, we compute the Curie temperatures for each compound, 942.48 K for Co3CuN, 692.7 K for Co3ZnN, and 1400.41 K for Fe3CuN, which are substantially elevated, indicating robust ferromagnetic behavior that persists well above ambient conditions. Mechanical properties, including stability, deformation behavior, and ductility, are validated through elastic calculations, with various mechanical anisotropy factors examined. From an application perspective, the thermoelectric characteristics of Co3CuN, Co3ZnN, and Fe3CuN are meticulously evaluated, focusing on parameters like the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor and figure of merit (zT). The analysis highlights promising power factor values of 3.0×1011(W/cm.K2), 4.0×1011(W/cm.K2), and 6.0×1011(W/cm.K2) for Co3CuN, Co3ZnN, and Fe3CuN, respectively, suggesting potential for enhanced efficiency in thermopower generation, particularly in waste heat recovery applications. Furthermore, the study provides a comprehensive analysis of the ground-state optical properties of A3XN, including the dielectric constant, photoconductivity, reflectivity, refractive index, absorption coefficient, and extinction coefficient. The reflectivity spectra demonstrate high reflectivity of 45 % across visible and ultravioletregions, suggesting suitability for applications in coatings designed to mitigate solar heating effects.

Unveiling the magnetic structure of BaFeO3-y: Shedding light on the elusive magnetic behavior

This work provides a comprehensive examination of the structural and magnetic properties of 6H-BaFeO2.96 over a wide temperature range (10 K < T < 300 K) using neutron and synchrotron X-ray diffraction. Additionally, the local oxidation state of iron is examined using electron energy loss spectroscopy. No structural changes that could indicate a charge-order transition are observed in spite of a reported possible charge disproportionation of Fe4+ into Fe(4+δ)+ and Fe(4-δ)+ phenomenon at low temperature. According to the magnetic characterization, BaFeO2.96 orders antiferromagnetically at TN=156 K. The application of external magnetic fields strongly influences the magnetic behavior; the transition temperature shifts to lower values with the applied magnetic field and the long-range magnetic order melts with an applied field of 14 T. The magnetocaloric effect clearly shows at TN a change from negative to positive magnetic entropy. The Rietveld refinement of the neutron powder diffraction data collected at 10 K, gives a magnetic ordering with propagation vector [0, 0, ½] and three magnetically distinct sites for the Fe atoms. This magnetic structure consists of ferromagnetic Fe-sheets perpendicular to the c-axis with the magnetic moments along the [110] direction coupled both ferromagnetic and antiferromagnetically along the c-axis. The magnetic moment values of the three Fe ions are very different evidencing a delicate equilibrium of competing magnetic interactions.

Effect of Atomic Vacancy Defect in h – BN Monolayer on Electronic Properties: A DFT Study

Abstract h-BN is a 2D material which also has considerable development potential in several fields. 2D materials such as h-BN are basically insulating materials but have unique properties and it would be good if they could be developed, especially to meet future energy needs or in the development of electronic devices. Therefore, the properties of h-BN are certainly needed to support this, one of which is the magnetic properties of h-BN. In this research, we modified the h-BN structure by providing defects in the form of vacancy defects by removing atoms in the h-BN layer. We modeled a monolayer h-BN with a supercell size of 4 x 4 x 1, and our calculations were carried out with Quantum ESPRESSO, which is based on density functional theory. The results we obtained showed the emergence of magnetic moment values in h-BN due to defects in the form of atomic vacancies. Furthermore, this research successfully illustrates how vacancy defects in h-BN can modify the band structure, leading to changes in electron behavior around the Fermi energy level.

Mechanism Behind the Enhanced Ferromagnetic Contributions Upon Ru Substitution in Ca3Mn2O7 from X-Ray Absorption Spectroscopies.

We have studied the local structure and electronic and magnetic properties of hybrid improper ferroelectric Ca3Mn2O7 upon Ru substitution at the Mn site by a combination of atomic-selective X-ray absorption spectroscopies in the soft and hard X-ray energy regimes. Ru substitution enhances the macroscopic ferromagnetic contributions, whose origin is here elucidated. In particular, soft X-ray magnetic circular dichroism (XMCD) data indicate that the spin moments of Mn and Ru are aligned in opposite directions, with the effective magnetic moments of Ru being about 1 order of magnitude smaller than for Mn. The XMCD results also demonstrate the presence of an intrinsic ferromagnetic component in the Mn sublattice for Ru contents x ≥ 0.3, although the values of the net Mn magnetic moment are much smaller than expected for a fully saturated Mn4+ magnetic sublattice. Soft and hard X-ray absorption spectroscopy measurements show that Mn keeps a +4 valence state independently of the Ru content, whereas Ru is in an intermediate valence state, ranging between +4.7 (x ≤ 0.1) and +4.4 (x ≥ 0.7). Analysis of the extended X-ray absorption fine structure (EXAFS) signals at the Mn and Ru K-edges suggests the lack of a complete solid solution in the local structure across the entire range of compositions. These findings disclose the existence of charge transfer between Mn and Ru atoms, so the weak ferromagnetic component is attributed to a canting of the antiferromagnetically ordered Mn4+ spins caused by the oxygen-mediated hybridization between localized Mn4+ 3d and itinerant intermediate valence Ru 4d bands, in analogy to the mechanism proposed for ferromagnetism in ordered doubled perovskites with 3d and 4d/5d transition-metal ions. In the present case, disorder prevents the formation of long-range ferromagnetism.

Detailed DFT based exploration on spin-gapless features of IrCoNbX (X=Al, Ga, In) alloys

An investigation has been conducted on the spin-polarized structural, electronic, charge transfer, −COHP and magnetic behaviour of IrCoNbX (X=Al, Ga, In) alloys. To corroborate the studied properties the generalized gradient approximation (GGA), modified Becke Johnson (mBJ) and DFT+U schemes within the framework of density functional theory. The structures found comparatively more stable in spin-polarized phase than non-spin polarized phase. Based on electronic band structure and electronic density of states’ analysis IrCoNbX alloys have demonstrated spin-gapless features in spin ↑ channel and semiconducting characteristics in spin ↓ channel. The −COHP examination revealed that Nb-Ir pair exhibited significantly stronger bonding interaction in comparison to XCo (XAl, Co, In, Nb) bonding pairs in IrCoNbX alloys. Each of the studied alloys manifested an integer value of the total magnetic moment of 2.0 μB/f.u under mBJ scheme. The findings of current study proposed the experimental investigation of these alloys for potential applications in spintronics field.

Study of magnetic, thermodynamic and transport properties of Laves phase NdRh[formula omitted]

The results of magnetic measurements, electron spin resonance, heat capacity, resistivity, and magnetocaloric effect as well as density functional theory (DFT), are presented for the compound NdRh2 (MgCu2-type structure). This compound was synthesized at a pressure of 8 GPa and a temperature of 1700 K. The magnetic properties of the material are shown to be determined by the high-temperature (over 400 K) spin polarization of the 4d Rh electrons and by the ferrimagnetic (FiM) interaction of Rh and Nd magnetic subsystems. Concurrently, the spontaneous magnetization of the spin polarization of 4d Rh electrons is ≈0.01μB/Rh, while the Nd magnetic moment is ≈1.7μB/Nd. This leads to complicated magnetic behavior with long range FiM order at TC≲7 K at zero field and with wide temperature range of spin fluctuations TC<T≲50 K. Specific heat and resistivity data provide corroboration of the spin fluctuation regime with the spin fluctuation temperature Θsf≈28.5 K. The optimal critical parameters were identified as β=1.18±0.02, γ=0.85±0.02, and TC≈40 K from modified Arrott plotting, which are distinct from any conventional universality class. The maximum magnetocaloric effect, when the magnetic field changes from 0 to 9 T, ΔH=9 T occurs at T≈11 K and the magnetic entropy change reaches −ΔSm=7.0 J (kg K)−1. In our DFT calculations, the FiM arrangement was obtained, with values of magnetic moments of Nd and Rh. Additionally, the Fermi surface was constructed.

Prediction of ferromagnetism in GaN:Ag and SiC:Ag nanotubes

Ferromagnetism in single-walled (6,0) GaN(SiC):Ag nanotubes were studied based on ab initio simulations within a pseudopotential method. For the GaN:Ag single-walled nanosystems, the width of the band gap reduces with the increase of dopant concentration. While Ag-doped SiC nanotubes, the band gap of majority-spin states decrease and these systems show metallic character. The first-principles results of total energies for SiC(GaN):Ag nanotubes predicted the stability of the ferromagnetic and antiferromagnetic phase, respectively. The obtained values of total magnetic moments of Ag-GaN and Ag-SiC systems are ∼2.0 and ∼3.2 μB, respectively. The analysis of the results of density of states show the significant contribution to the magnetization of both defected GaN:Ag and SiC:Ag systems come from three nitrogen and carbon atoms which are bonded with the dopant. First-principles investigation, suggest that the SiC(GaN):Ag nanotubes can be made into magnetic materials, and these are promising candidates for electronic, optoelectronic, and spintronic devices.

Cascade Ξ0 baryon spectroscopy in the relativistic framework of an independent quark model

The spectroscopy of Ξ0 is performed within the relativistic framework of independent quark model. The equal mixture of scalar and vector components in the potential having Martin-like form is considered for the confinement. With the suitable potential parameters for Ξ0, mass spectra for high radial and orbital excitation is calculated. The experimentally observed values of the ground-state magnetic moment, branching ratios, and asymmetry parameters for radiative weak decays, Ξ0→Λ0+γ0 and Ξ0→Σ0+γ0 are obtained to validate the model. The spin parity of experimentally known resonances like Ξ(1530), Ξ(1820), and Ξ(2030) are confirmed through the Regge trajectories in (J,M2) plane. The spin parity of Ξ(1950), Ξ(2130), and Ξ(2250) are predicted using those Regge trajectories. The radiative decay width and magnetic moment of first resonance is also predicted. Published by the American Physical Society 2024

Impact of Fe-doping on magneto-optoelectronic properties of beryllium sulfide (BeS): A first principles insight

The investigation of electronic, magnetic, structural, and optical properties of Be1-xFexS alloys is carried out by utilizing FP-LAPW method based on density functional theory (DFT) calculations. Fe-doped BeS exhibits half-metallic ferromagnetic behaviour at all doping concentrations, transforming it as favourable contender for spintronic devices. Our findings reveal the presence of 100 % spin polarization of electronic states. The calculated values of magnetic moments are 4.0, 8.0, and 16.0 μB for Be0.9375Fe0.0625S, Be0.875Fe0.125S and Be0.75Fe0.25S, respectively. The pristine BeS compound adopts a cubic close packing structure, known as the zinc blende structure, with the space group F-43m. The static values of R(0) are observed to be 0.21, 0.56, and 0.72 for Fe doped BeS at Be0.9375Fe0.0625S, Be00875Fe0.125S and Be0.75Fe0.25S, respectively. The maximum values of σ(ω) are computed as 16375.9 (1/Ω cm) for 6.25 %, 14336.5 (1/Ω cm) for 12.5 %, and 11002.1 (1/Ω cm) for 25 % Fe doped BeS. The present study unveils maximum optical absorption and conductivity in the ultraviolet (UV) region, suggesting its potential application in UV-based photovoltaic devices.

Structural, wide band gap half-metallic, and pressure-dependent thermodynamic predictions of Li2TMMgO6 (TM = V, Nb, and Ta) double perovskites.

Li2VMgO6, Li2NbMgO6, and Li2TaMgO6 double perovskite compounds were energetically the most stable in the FM phase. The lattice constants were 7.63Å, 7.94Å, and 7.95Å, and the Curie temperatures were 910.451K, 930.739K, and 1258.821K, respectively. The wide bandgap semiconductor characters were provided in the GGA-PBE methods as 2.139eV, 4.209eV, and 5.007eV, respectively. This wide band gap semiconductor state in the majority carriers and the metallic state in the minority states made these double perovskites true half-metallic ferromagnetics. The bulk modulus obtained in the ground state calculations and the values obtained from thermodynamic calculations were relatively close. Debye temperatures in the initial state conditions were 747K, 685.13K, and 587.77K, respectively. The total magnetic moment values were calculated as 3.00 µB/f.u. The most significant contribution to this value came from oxygen atoms. The theoretical calculations of Li2VMgO6, Li2NbMgO6, and Li2TaMgO6 double perovskite alloys were performed using the WIEN2k program developed by Blaha et al. The electronic calculations were made with GGA-PBE, GGA + mBJ, and GGA + U approximations in the space number 225 and the Fm-3m symmetry group. The thermodynamic calculations were performed using Gibbs2. In thermodynamic calculations, temperature increases were determined as 100K and temperature values were increased from 0 to 1200K.

NICA Facilities for the Search for EDM Light Nuclei

To search for proton Electric Dipole Moments (EDM) using proton storage ring with purely electrostatic elements, the concept of frozen spin method has been proposed by Brookhaven National Laboratory. This method is based on two facts: in the equation of spin precession, the magnetic field dependence is entirely eliminated, and at the ‘‘magic’’ energy, the spin precession frequency coincides with the precession frequency of the particle momentum. In case of deuteron, we have to use the electrical and magnetic field simultaneously, keeping the frozen spin direction along the momentum as in the pure electrostatic ring. Later, Yu. Senichev proposed the concept of quasi-frozen spin, in which the spin oscillates around the direction of the pulse within half the value of the advanced phase of rotation in magnetic arcs, each time returning back in deflectors with an electrostatic field. Due to the low value of the anomalous magnetic moment of deuteron, an effective contribution to the expected EDM effect is reduced only by a few percent compared with frozen spin method. In this work, we consider the adapted structure of the NICA and Nuclotron synchrotrons, in which the ‘‘quasi-frozen spin’’ option can be implemented. The advantage of the ‘‘quasi-frozen spin’’ concept is the possibility of using synchrotrons already existing in the world that are not focused on studying EDM, which makes this method the only one possible for the accelerators of the NICA complex.

Influence of anti-ferromagnetic ordering and electron correlation on the electronic structure of MnTiO3

Electron correlation and long-range magnetic ordering have a significant impact on the electronic structure and physical properties of solids. Here, we investigate the electronic structure of ilmenite MnTiO3 using room temperature photoemission spectroscopy and theoretical approaches within density functional theory (DFT), DFT+ U and DFT+dynamical mean-field theory (DMFT). Mn 2p (Ti 2p) core level photoemission spectra, confirming Mn2+ (Ti4+) oxidation state, exhibit multiple satellites which are very similar to that of MnO (TiO2), suggesting similar strength of various interactions in this system. Valence band spectra collected at different photon energies suggest dominant Mn 3d character in the highest occupied band with a wide insulating gap. DFT(+ U) correctly predicts the experimentally observed anti-ferromagnetic (AFM) insulating ground state for MnTiO3 where the requirement of a large U to reproduce the experimental values of magnetic moment and band gap signifies the importance of electron correlation. Magnetically disordered paramagnetic (PM) phase could be well captured within DFT+DMFT, which provides an excellent agreement for the experimental band gap, paramagnetic moment, valence band spectra as well as dominant Mn 3d character in the highest occupied band. The calculated spectral function remains largely unaffected and exhibits sharper features in the magnetically ordered AFM phase. We show that the electronic structure of MnTiO3 in both the PM and AFM phases can be accurately described within DFT+DMFT.

First constraints on the Lμ− Lτ explanation of the muon g-2 anomaly from NA64-e at CERN

The inclusion of an additional U(1) gauge Lμ − Lτ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light Z′ vector boson, with dominant coupling to μ and τ leptons and interacting with electrons via a loop mechanism. The Lμ − Lτ model can also explain the Dark Matter relic abundance, by assuming that the Z′ boson acts as a “portal” to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the Z′ search performed by the NA64-e experiment at CERN SPS, that collected ~ 9 × 1011 100 GeV electrons impinging on an active thick target. Despite the suppressed Z′ production yield with an electron beam, NA64-e provides the first accelerator-based results excluding the g − 2 preferred band of the Z′ parameter space in the 1 keV <mZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{Z^{\\prime }} $$\\end{document} ≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64-μ experiment with a muon beam.

The half-metallicity, thermoelectric and optoelectronic attributes of K2CeB’X6 (B’=Ag, Cu & X=Cl, Br) for spintronics and renewable energies: A spin-polarized DFT study

The distinctive electronic characteristics of half-metallic materials make them exceptional as they pave the way for innovations in spintronics and other magnetic fields. We predict the ferromagnetism in half-metallic K2CeB’X6 (B’ = Ag, Cu & X = Cl, Br) perovskite halides by employing the spin-polarized computations. The tolerance factor, formation energies and optimization plots favor the structural stability of all perovskites. The K2CeB’X6 (B’ = Ag, Cu & X = Cl, Br) are half-metallic with a direct band gap of 2.59 eV, 2.53eV and 1.05eV, respectively, in the spin-down state, while the spin-up exhibit metallic character. The magnetic behavior is confirmed by the magnetic moment values. Several parameters for optical response are computed, showing the absorption in the visible and high energy spectrum. The spin-polarized response in terms of thermoelectric characteristics shows outstanding results. We have achieved the highest ZT values in spin-dn channel, which is unity for K2CeAgCl6, K2CeAgBr6 and 0.98 for K2CeCuCl6 at 300K. These values are continued even at higher temperatures with no significant change. The half-metallic characteristics with excellent thermoelectric attributes in the spin-dn channel provide the evidence to utilize these perovskites for spintronics and green technologies.

Computational investigation of elastic properties of hypothetical Half-Heusler compounds XNbSn under hydrostatic pressures

We investigated the electronic, elastic, and magnetic properties of the hypothetical half- Heusler alloys with Niobium base atom, XNbSn with (X= Cr, Mn, Co, Fe, V) uses the full-potential (linearized) augmented plane-wave and local-orbitals [FP-(L)APW + lo] basis set in the WIEN2K ab-initio package based on density functional theory (DFT). We investigated the elastic constants, Shear modulus, young modulus, and bulk modulus of these alloys under different pressures (0, 20, 40, and 80 GPa). We predicted that CoNbSn behaves as a semiconductor with a direct energy gap of 0.99 eV, while the other half- Heusler alloys show a metallic behavior. CoNbSn keeps its semiconductor behavior under higher pressures up to 80 GPa. Both of VNbSn and CrNbSn have a high value of magnetic moments of 2.158 and 3.002 µB respectively. All XNbSn alloys are stable mechanically at different pressures according to the Born-Huang conditions. CoNbSn, FeNbSn, CrNbSn, and MnNbSn behave as a ductile material at ambient pressure.

Spin-polarized DFT investigations of novel KVSb half-Heusler compound for spintronic and thermodynamic applications

In this study we have investigated the robust phase stability, elasto-mechanical, thermophysical and magnetic response of KVSb half Heusler compound by implementing density functional theory (DFT) models in WIEN2k simulation package. The dynamic phase stability is computed in phase type I, II & III phase configurations by optimising their energy. It is observed that given compound is more stable in spin-polarized state of phase type-III. To explore the electronic band structure, we apply the generalised gradient approximation along with Hubbard potential U. The electronic band profile of the Heusler alloy display a half-metallic nature. Moreover, the calculated second-order elastic parameters divulge the brittle nature. To understand the thermodynamical and thermoelectric stability of the alloy at various temperature and pressures ranges Quasi-Harmonic Debye model is executed successfully. The computed value of magnetic moment (MM) found in good agreement with Slater-Pauling rule. Our findings confirms that the predicted half Heusler alloy can be used in various spintronics and thermoelectric applications.

Exploring magnetic space groups of [formula omitted] MXene and its connection to vibrational and electronic properties

The vibrational, electronic, and magnetic properties of two-dimensional Cr2N MXene were investigated. Two crystal cells (hexagonal and monoclinic) were considered with their respective magnetic space groups. In the absence of experimental data to fine-tune the Ueff (Hubbard correction), we utilized cell parameters and magnetic moment as a reference window, derived from meta-GGA calculations performed with the SCAN functional. A value of Ueff (1.25 eV) was determined, which does not overestimate the lattice parameters and magnetic moment values. Phonon scattering was calculated, and the vibrational modes were indexed. According to the density of states, the observed splitting in the eg and t2g orbitals, and the crystal field analysis, we deduce that chromium in the MXene Cr2N predominantly adopts an octahedral coordination environment, a combination of octahedral and tetrahedral coordination results in the splitting of the d orbitals. Finally, using Monte Carlo simulation, the critical temperature (Tc) for each space group with different functionals was obtained.

Structural, magnetic and photoluminescence properties of Zn-Ni ferrites synthesized by hydrothermal method

Nanocrystalline ZnxNi1-xFe2O4 (0 ≤ x ≤ 1.0) ferrites were synthesized by hydrothermal method. XRD analysis showed that all compositions crystallize with a cubic spinel-type structure with an average crystallite size in the range of 17–27 nm which corresponded to particle sizes obtained from TEM. The lattice parameter increased from 8.289 to 8.432 Å with increasing Zn content. The ZnxNi1-xFe2O4 nanoferrites exhibit superparamagnetic behaviour at room temperature (RT). The saturation magnetization (Ms) varies considerably with Zn content to reach a maximum value for Zn0.5Ni0.25Fe2O4 composition, i.e. 41.893 emu/g. The high Ms and magnetic moment values are attributed to cation distribution change. The electron spin resonance (ESR) results demonstrated g-values ranging between 2.005 and 2.621 which indicated strong exchange interaction between nanoparticles, type of morphology, and crystalline nature of particles. These low g-values make ZnxCo1-xFe2O4 nanoferrites suitable for applications in low-frequency devices. The Mössbauer spectroscopy results revealed the transition from ferromagnetic to paramagnetic state, by showing collapse of sestet to quadrupole doublet. The optical properties of the nanoferrites were investigated photoluminescence (PL) spectra. The broad visible emission band at 427 nm (2.90 eV), 471 nm (2.60 eV) and 520 nm (2.38 eV) were observed in all PL spectra. The electron spin resonance and photoluminescence results show that Zn-Ni ferrites are good candidates for blue LEDs and in gas sensing applications.

Supramolecular Polymerization as a Tool to Reveal the Magnetic Transition Dipole Moment of Heptazines.

Heptazine derivatives have attracted significant interest due to their small S1-T1 gap, which contributes to their unique electronic and optical properties. However, the nature of the lowest excited state remains ambiguous. In the present study, we characterize the lowest optical transition of heptazine by its magnetic transition dipole moment. To measure the magnetic transition dipole moment, the flat heptazine must be chiroptically active, which is difficult to achieve for single heptazine molecules. Therefore, we used supramolecular polymerization as an approach to make homochiral stacks of heptazine derivatives. Upon formation of the supramolecular polymers, the preferred helical stacking of heptazine introduces circular polarization of absorption and fluorescence. The magnetic transition dipole moments for the S1 ← S0 and S1 → S0 are determined to be 0.35 and 0.36 Bohr magneton, respectively. These high values of magnetic transition dipole moments support the intramolecular charge transfer nature of the lowest excited state from nitrogen to carbon in heptazine and further confirm the degeneracy of S1 and T1.