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We introduce FCclasses3, a code to carry out vibronic simulations of electronic spectra and nonradiative rates, based on the harmonic approximation. Key new features are: implementation of the full family of vertical and adiabatic harmonic models, vibrational analysis in curvilinear coordinates, extension to several electronic spectroscopies and implementation of time-dependent approaches. The use of curvilinear valence internal coordinates allows the adoption of quadratic model potential energy surfaces (PES) of the initial and final states expanded at arbitrary configurations. Moreover, the implementation of suitable projectors provides a robust framework for defining reduced-dimensionality models by sorting flexible coordinates out of the harmonic subset, so that they can then be treated at anharmonic level, or with mixed quantum classical approaches. A set of tools to facilitate input preparation and output analysis is also provided. We show the program at work in the simulation of different spectra (one and two-photon absorption, emission and resonance Raman) and internal conversion rate of a typical rigid molecule, anthracene. Then, we focus on absorption and emission spectra of a series of flexible polyphenyl molecules, highlighting the relevance of some of the newly implemented features. The code is freely available at http://www.iccom.cnr.it/en/fcclasses/, Ministerio de Ciencia e Innovacion, Grant/Award Number: PID2019-110091GB-I00; Ministerio de Universidades, Plan de Recuperacion, Transformación y Resiliencia, Grant/Award Number: CA2/RSUE/2021-00890; Universidad Autonoma de Madrid

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

Oxidation states are integer in number but dn configurations of transition metal centers vary continuously in polar bonds. We quantify the shifts of the iron L3 excitation energy, within the same formal oxidation state, in a systematic L edge X ray absorption spectroscopy study of diatomic gas phase iron II halide cations, [FeX] ,where X F, Cl, Br, I. These shifts correlate with the electronegativity of the halogen, and are attributed exclusively to a fractional increase in population of 3d derived orbitals along the series as supported by charge transfer multiplet simulations and density functional theory calculations. We extract an excitation energy shift of 420 meV 60 meV spanning the full range of possible 3d occupations between the most ionic bond in [FeF] and covalently bonded [FeI]

Research on the chiral magneto-optical properties of inorganic nanomaterials has enabled novel applications in advanced optical and electronic devices. However, the corresponding chiral magneto-optical responses have only been studied under strong magnetic fields of ≥1 T, which limits the wider application of these novel materials. In this paper, we report on the enhanced chiral magneto-optical activity of supra-assembled Fe3O4 magnetite nanoparticles in the visible range at weak magnetic fields of 1.5 mT. The spherical supra-assembled particles with a diameter of ∼90 nm prepared by solvothermal synthesis had single-crystal-like structures, which resulted from the oriented attachment of nanograins. They exhibited superparamagnetic behavior even with a relatively large supraparticle diameter that exceeded the size limit for superparamagnetism. This can be attributed to the small size of nanograins with a diameter of ∼12 nm that constitute the suprastructured particles. Magnetic circular dichroism (MCD) measurements at magnetic fields of 1.5 mT showed distinct chiral magneto-optical activity from charge transfer transitions of magnetite in the visible range. For the supraparticles with lower crystallinity, the MCD peaks in the 250-550 nm range assigned as the ligand-to-metal charge transfer (LMCT) and the inter-sublattice charge transfer (ISCT) show increased intensities in comparison to those with higher crystallinity samples. On the contrary, the higher crystallinity sample shows higher MCD intensities near 600-700 nm for the intervalence charge transfer (IVCT) transition. The differences in MCD responses can be attributed to the crystallinity determined by the reaction time, lattice distortion near grain boundaries of the constituent nanocrystals, and dipolar interactions in the supra-assembled structures.

Synchrotron radiation based X-ray scattering techniques provide powerful bulk-sensitive probes for actinide materials. Here, selected experiments showing the potential of these techniques in advancing the knowledge of actinides and their compounds are reviewed., By reviewing a selection of X-ray diffraction (XRD), resonant X-ray scattering (RXS), X-ray magnetic circular dichroism (XMCD), resonant and non-resonant inelastic scattering (RIXS, NIXS), and dispersive inelastic scattering (IXS) experiments, the potential of synchrotron radiation techniques in studying lattice and electronic structure, hybridization effects, multipolar order and lattice dynamics in actinide materials is demonstrated.

Prussian blue analogue nanocrystals of the CsINiII[CrIII(CN)6] cubic network with 6 nm size were assembled as a single monolayer on highly organized pyrolytic graphite (HOPG). X-ray magnetic circular dichroism (XMCD) studies, at the Ni and Cr L2,3 edges, reveal the presence of an easy plane of magnetization evidenced by an opening of the magnetic hysteresis loop (coercive field of ≈200 Oe) when the magnetic field, B, is at 60° relative to the normal to the substrate. The angular dependence of the X-ray natural linear dichroism (XNLD) reveals both an orientation of the nanocrystals on the substrate and an anisotropy of the electronic cloud of the NiII and CrIII coordination sphere species belonging to the nanocrystals' surface. Ligand field multiplet (LFM) calculations that reproduce the experimental data are consistent with an elongated tetragonal distortion of surface NiII coordination sphere responsible for the magnetic behavior of monolayer.

It is well-known that treatment of β-octaethylporphyrin with H2 O2 /conc. H2 SO4 converts it to a β-oxochlorin as well as all five constitutional isomers of the corresponding β,β'-dioxo-derivatives: two bacteriochlorin-type isomers (β-oxo groups at opposite pyrrolic building blocks) and three isobacteriochlorin-type isomers (β-oxo-groups at adjacent pyrrolic building blocks). By virtue of the presence of the strongly electronically coupled β-oxo auxochromes, none of the chromophores are archetypical chlorins, bacteriochlorins, or isobacteriochlorins. Here the authors present, inter alia, the single crystal X-ray structures of all free-base diketone isomers and a comparative description of their UV-vis absorption spectra in neutral and acidic solutions, and fluorescence emission and singlet oxygen photosensitization properties, Magnetic Circular Dichroism (MCD) spectra, and singlet excited state lifetimes. DFT computations uncover underlying tautomeric equilibria and electronic interactions controlling their electronic properties, adding to the understanding of porphyrinoids carrying β-oxo functionalities. This comparative study lays the basis for their further study and utilization.

We investigate the surface oxidation in a van der Waals ferromagnet Fe3-xGeTe2, a material widely utilized for spintronic applications. While known for its relative air-insensitivity, exposure to air during the handling process (e.g. device or heterostructure fabrication) can lead to reduction or disappearance of its magnetic signal. Comparison of x-ray absorption and x-ray magnetic circular dichroism spectra between pristine and air-exposed Fe3-xGeTe2 confirm a naturally oxidized surface layer on the material. The surface oxide layer has predominantly Fe3+ content. X-ray absorption spectroscopy done on micron-sized exfoliated Fe3-xGeTe2 flakes reveal that the change in the surface chemical properties can be quite significant for thin flakes. The surface modulation of Fe3-xGeTe2 can lead to inaccuracies in characterizing its interfacial magnetic and spin transport properties, and complicate device and heterostructure fabrication processes.

Characteristic features of magnetoplasmonic responses in higher-order multipolar (quadrupolar and octupolar) modes of Ag nanoparticles (from 90 to 200 nm in diameter) are demonstrated for the first time using magnetic circular dichroism (MCD) spectroscopy. In optical extinction spectra, with an increase in the size of the nanoparticles, the red shift of dipolar plasmon peaks and the appearance of higher-order multipolar resonances can reasonably be observed. Aside from the dipolar and quadrupolar modes, the octupolar plasmonic extinction is very weak and almost unresolved. In contrast, strikingly, MCD shows a very sharp and intense peak (or valley) for the octupolar resonance, meaning its unique properties with high sensitivity and enhanced spectral resolution. MCD responses assignable to the quadrupolar mode have a distinct derivative-like shape, which is different from those observed for Ag nanocubes and nanodecahedra in our previous studies. We then discuss this behavior from the viewpoint of size and/or polyhedral shape inhomogeneity.

Circularly polarized sources of radiation play a vital role in photoelectron circular dichroism and magnetic circular dichroism experiments. While circularly polarized radiation can be routinely generated in the visible domain of the electromagnetic spectrum due to the availability of laser sources and optics in this range, generation of circularly polarized radiation in the extreme ultraviolet (XUV) domain is challenging and, using table-top sources it is currently limited to high harmonic generation from gases using bi-circular, complicated two-source and/or interferometry arrangement. In this work, being fueled by recent development of high harmonic generation and spectroscopy of solids, we demonstrate the generation of circularly polarized extreme ultraviolet light using interaction of intense circularly polarized drivers. The simplicity of our experimental setup enables rapid application of circularly polarized XUV light in circular dichroism experiments.

We present an implementation of the [Formula: see text] term of Magnetic Circular Dichroism (MCD) within the Algebraic Diagrammatic Construction (ADC) scheme of the polarization propagator and its Intermediate State Representation. As illustrative results, the MCD spectra of the ADC variants ADC(2), ADC(2)-x, and ADC(3) of the molecular systems uracil, 2-thiouracil, 4-thiouracil, purine, hypoxanthine 1,4-naphthoquinone, 9,10-anthraquinone, and 1-naphthylamine are computed and compared with results obtained by using the Resolution-of-Identity Coupled-Cluster Singles and Approximate Doubles method, with literature Time-Dependent Density Functional Theory results, and with available experimental data.

Large magnetic optical rotary dispersion (Faraday rotation) has been demonstrated recently in methylammonium lead bromide. Here, we investigate the prospect of extending the active spectral range by altering the halogen. We also investigate the origins of large Faraday rotation in these diamagnetic materials using magnetic circular dichroism (MCD) spectroscopy and the Kramers-Kronig relations. We find that, while MAPbCl3 (MA = methylammonium) single crystals exhibit a large Verdet constant in the blue, no appreciable Faraday rotation is observed in the red/near infra-red for MAPbI3 single crystals. However, in all film samples, we find clear evidence of large MCD resulting from the Zeeman splitting of the highly resonant 1s exciton state. Our Kramers-Kronig calculations of Faraday rotation based on MCD data matches well with the dispersion of our experimental data for MAPbCl3 and MAPbBr3 , with some deviation in magnitude-demonstrating the excitonic nature of Faraday rotation in these materials. However, our calculations predict significant Faraday rotation in MAPbI3 , contrary to our experimental results, indicating a potential discrepancy between the properties of the thin film and single crystal.

Fe3O4 thin films on Si (100) substrate were prepared by chemical solution deposition (CSD) technique. In the present work, we have investigated the control of magnetization of Fe3O4 thin films by N2 ion implantation. The dosage of N2 ion implantation in Fe3O4 thin films varies from 0 to 3 × 1016 ions/cm2. The magnetization decreased as a function of dosage concentration that changed the electronic and magnetic properties of the thin films. Advanced characterization techniques, such as X-ray absorption spectroscopy (XAS) X-ray magnetic circular Dichroism (XMCD), were used for the first time to estimate the electronic and magnetic properties of the thin films in surface-sensitive total electron-yield mode. The temperature-dependent XMCD measurement suggests that with an increase in the dosage of N2 from 0 to 3 × 1016 ions/cm2, Fe3O4 transitioned from a high-magnetization phase to a low magnetization phase. The observation was further supported by vibrating sample magnetometer (VSM) measurements, which pointed toward the same magnetic-phase transition in the films.

By the bridging action of the 6-chloro-2-hydroxypyridine (Hchp) ligand and the terminal coordination role of the homochiral ligand, (-)/(+)-3-trifluoroacetyl camphor (l-Htfc/d-Htfc), a pair of enantiomerically pure dysprosium(III) dinuclear complexes, [Dy2(l-tfc)4(chp)2(MeOH)2] (l-1) and [Dy2(d-tfc)4(chp)2(MeOH)2] (d-1), was obtained. Their circular dichroism (CD) spectra verified their enantiomeric nature. Magnetic investigation indicated that they exhibit ferromagnetic interaction and good zero field single-molecule magnet (SMM) properties. The Ueff/k values of l-1 and d-1 at 0 Oe are 180.5 and 181.3 K, respectively, which are large values for homochiral Dy(III) SMMs. A reasonable explanation for the magnetic properties of l-1 and d-1 was supplied by ab initio calculations. Remarkably, magnetic circular dichroism (MCD) investigation revealed that the chiral Dy2 enantiomers show a strong magneto-optical Faraday effect at room temperature, suggesting potential applications in magneto-optical devices.

Voltage control of magnetic order is desirable for spintronic device applications, but 180° magnetization switching is not straightforward because electric fields do not break time-reversal symmetry. Ferrimagnets are promising candidates for 180° switching owing to a multi-sublattice configuration with opposing magnetic moments of different magnitudes. In this study we used solid-state hydrogen gating to control the ferrimagnetic order in rare earth–transition metal thin films dynamically. Electric field-induced hydrogen loading/unloading in GdCo can shift the magnetic compensation temperature by more than 100 K, which enables control of the dominant magnetic sublattice. X-ray magnetic circular dichroism measurements and ab initio calculations indicate that the magnetization control originates from the weakening of antiferromagnetic exchange coupling that reduces the magnetization of Gd more than that of Co upon hydrogenation. We observed reversible, gate voltage-induced net magnetization switching and full 180° Neel vector reversal in the absence of external magnetic fields. Furthermore, we generated ferrimagnetic spin textures, such as chiral domain walls and skyrmions, in racetrack devices through hydrogen gating. With gating times as short as 50 μs and endurance of more than 10,000 cycles, our method provides a powerful means to tune ferrimagnetic spin textures and dynamics, with broad applicability in the rapidly emerging field of ferrimagnetic spintronics. Voltage control of magnetic order is one of the keys to energy-efficient spintronic applications. Voltage gating using a solid-state hydrogen pump now allows for reversible control of ferrimagnetic order, external-field-free 180° magnetic switching and ferrimagnetic spin texture writing.

We report on the electronic structure and magnetic properties of hybrid heterostructures combined the ferromagnetic double perovskite Sr2CrOsO6 (SCOsO) and ferroelectric BaTiO3 (BTO) calculated in the GGA approach using the fully relativistic spin-polarized Dirac LMTO method. The electronic band structure is studied in the BTO and SCOsO oxides as well as in SCOsO/BTO hetero structures with different supercells: (1 × 1 × 1) monolayered, (2 × 2 × 1), and (1 × 1 × 2) SCOsO/BTO heterostructures. The optical and magneto-optical spectra of pure BTO and SCOsO oxides as well as of the SCOsO/BTO heterostructures are investigated theoretically and compared with avaliable experimental data. The element-specific x-ray absorption spectra as well as the x-ray magnetic circular dichroism at the Ti, Ba, and Os L2,3 edges in SCOsO/BTO heterostructures are investigated theoretically. Good agreement with experimental spectra has been found.

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

Recent discoveries of intrinsic two-dimensional (2D) magnets open up vast opportunities to address fundamental problems in condensed matter physics, giving rise to applications from ultra-compact spintronics to quantum computing. The ever-growing material landscape of 2D magnets lacks, however, carbon-based systems, prominent in other areas of 2D research. Magnetization measurements of the Eu/graphene compound—a monolayer of the EuC6 stoichiometry—reveal the emergence of 2D ferromagnetism but detailed studies of competing magnetic states are still missing. Here, we employ element-selective X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) to establish the magnetic structure of monolayer EuC6. The system exhibits the anomalous Hall effect, negative magnetoresistance, and magnetization consistent with a ferromagnetic state but the saturation magnetic moment (about 2.5 µB/Eu) is way too low for the half-filled f-shells of Eu2+ ions. Combined XAS/XMCD studies at the Eu L3 absorption edge probe the EuC6 magnetism in high fields and reveal the nature of the missing magnetic moments. The results are set against XMCD studies in Eu/silicene and Eu/germanene to establish monolayer EuC6 as a prominent member of the family of Eu-based 2D magnets combining the celebrated graphene properties with a strong magnetism of europium.

In order to disentangle the physical effects at the origin of transition metal K-edge X-ray magnetic circular dichroism (XMCD) in coordination polymers and quantify small structural distortions from the intensity of these signals, a systematic investigation of Prussian blue analogs as model compounds is being conducted. Here the effects of the temperature and of the external magnetic field are tackled; none of these external parameters modify the shape of the XMCD signal but they both critically modify its intensity. The optimized experimental conditions, as well as a reliable and robust normalization procedure, could thus be determined for the study of the intrinsic parameters. Through an extended discussion on measurements on other XMCD-dedicated beamlines and for other coordination compounds, we finally provide new transition metal K-edge XMCD users with useful information to initiate and successfully carry out their projects.

The Faraday effect is a magneto-optical (MO) phenomenon that causes the plane of linearly polarized light to rotate when passing through a medium subjected to a parallel magnetic field. Informed by the established quantum mechanical model developed by Buckingham and Stephens, we sought to identify molecules that would exhibit large MO responses. Magnetic circular dichroism studies of ferrocenium in the 1970s revealed its potential as an MO material; however, it has not been evaluated in the context of Faraday rotation and thin-film optical applications. Herein, we report near-infrared (NIR) Faraday rotation in thin films of decamethylferrocenium/poly(methyl methacrylate) composites with maximum Verdet constants of -3.45 × 104 deg T-1 m-1 at 810 nm (absorbance = 0.09) and -1.44 × 104 deg T-1 m-1 at 870 nm (absorbance = 0.01). These polymer-metallocene thin films deliver larger Verdet constants than commercially used NIR inorganic Faraday rotators and are facile and inexpensive to produce. The temperature dependence and distinct lineshape of the MO responses observed in decamethylferrocenium radical cations, decamethylmanganocene, and chromocene are in accordance with the quantum mechanical model. The observation of a strong C-term Faraday rotation in solid-state organometallic materials provides the groundwork for the development of high-performance metallocene-based Faraday rotators.

Fe3GeTe2/MnPS3 and Fe3GeTe2/MnPSe3 van der Waals heterostructures were fabricated by mechanical exfoliation. Via the magneto-optical Kerr effect and reflected magnetic circular dichroism measurements, we have observed nearly three times enhancement of the coercive field, improvement of Curie temperature, and exchange bias effect in both heterostructures. These observations may provide new insights into the emergent heterostructure devices between itinerant ferromagnets and metal thio- and selenophosphates for both applied and fundamental research studies in magnetic correlations.

Current-induced magnetization switching by spin-orbit torque generated in heavy metals offers an enticing realm for energy-efficient memory and logic devices. The spin Hall efficiency is a key parameter in describing the generation of spin current. Recent findings have reported enhancement of spin Hall efficiency by mechanical strain, but its origin remains elusive. Here, we demonstrate a 45% increase in spin Hall efficiency in the platinum/cobalt (Pt/Co) bilayer, of which 78% of the enhancement was preserved even after the strain was removed. Spin transparency and X-ray magnetic circular dichroism revealed that the enhancement was attributed to a bulk effect in the Pt layer. This was further confirmed by the linear relationship between the spin Hall efficiency and resistivity, which indicates an increase in skew-scattering. These findings shed light on the origin of enhancement and are promising in shaping future utilization of mechanical strain for energy-efficient devices. Agency for Science, Technology and Research (A*STAR) Economic Development Board (EDB) National Research Foundation (NRF) Submitted/Accepted version This work is supported by an Industry-IHL Partnership Program (NRF2015-IIP001-001) and an EDB-IPP (RCA − 17/284) grant. This work is also supported by the RIE2020 ASTAR AME IAF-ICP grant (No. I1801E0030). W.Z. and P.K.J.W. acknowledge financial support by the Fundamental Research Funds for the Central Universities.

Greigite (Fe3S4) nanoparticles (NPs) were fabricated by the thermal decomposition method using two different surfactants: oleylamine (OLA) and 1-hexadecylamine (HDA). In both cases, the synthesized NPs were characterized as the Fe3S4 nanocrystals with minor inclusions of Fe9S11 phase. FT-IR spectroscopy and thermo-gravimetric analysis allow concluding about OLA or HDA shells covering magnetic core of NPs. Mossbauer spectra has revealed deviations of iron ions distribution among crystal positions from that presented in literature for pure greigite. In accordance with these deviations, the pronounce changes are observed in the magnetic circular dichroism (MCD) spectra which manifest themselves as the spectrum shift to higher energies of electromagnetic waves and redistribution of the MCD maximum intensities. These effects are associated with a change in the density of electronic states in the samples due to the redistribution of iron ions between octahedral and tetrahedral positions in nanocrystals under the influence of surfactants.

Cyclo[9]pyrrole, a ring-expanded porphyrin without meso-bridges and having an odd number of pyrroles, was synthesized via the oxidative coupling of 2,2':5',2″-terpyrrole. X-ray crystallography showed a C2-like symmetry with a large root-mean-square deviation. The optical properties and electronic structures were analyzed using magnetic circular dichroism spectroscopy and time-dependent density functional theory calculations.

Cocrystallization of different metal nanoclusters facilitates the preparation of cluster-based nanomaterials with enhanced properties. Herein, two pairs of enantiomeric 3d-4f cocrystallization structures of clusters R/S-[Mn10Ln6] and R/S-[Mn6Ln2] (Ln = Dy for 1R and 1S, Y for 2R and 2S) have been reported. Compounds R/S-[Mn10Ln6][Mn6Ln2] exhibit a large optical activity and magneto-optic effect as verified by natural circular dichroism (NCD) and magnetic circular dichroism (MCD). In addition, alternating current (ac) magnetic measurements show that the chiral R/S-[Mn10Dy6][Mn6Dy2] cocrystallization structure displays slow magnetic relaxation with Ueff = 25.1 K.

A UHV-compatible MOKE magnetometer for in situ studies operating in tandem with the PEEM at the Nanospectroscopy beamline of the Elettra synchrotron., We report on a custom-built UHV-compatible Magneto-Optical Kerr Effect (MOKE) magnetometer for applications in surface and materials sciences, operating in tandem with the PhotoEmission Electron Microscope (PEEM) endstation at the Nanospectroscopy beamline of the Elettra synchrotron. The magnetometer features a liquid-nitrogen-cooled electromagnet that is fully compatible with UHV operation and produces magnetic fields up to about 140 mT at the sample. Longitudinal and polar MOKE measurement geometries are realized. The magneto-optical detection is based on polarization analysis using a photoelastic modulator. The sample manipulation system is fully compatible with that of the PEEM, making it possible to exchange samples with the beamline endstation, where complementary X-ray imaging and spectroscopy techniques are available. The magnetometer performance is illustrated by experiments on cobalt ultra-thin films, demonstrating close to monolayer sensitivity. The advantages of combining in situ growth, X-ray Magnetic Circular Dichroism imaging (XMCD-PEEM) and MOKE magnetometry into a versatile multitechnique facility are highlighted.

It is our great pleasure to introduce the Festschrift of Chemistry to honor professor Josef Michl (Figure 1) on the occasion of his 80th birthday and to recognize his exceptional contributions to the fields of organic photochemistry, quantum chemistry, biradicals and biradicaloids, electronic and vibrational spectroscopy, magnetic circular dichroism, silicon and boron chemistry, supramolecular chemistry, singlet fission, and molecular machines [...]

Spin polarisation is found in the centrosymmetric nonferromagnetic crystals, chiral mesostructured NiO films (CMNFs), fabricated through the symmetry-breaking effect of a chiral molecule. Two levels of chirality were identified: primary nanoflakes with atomically twisted crystal lattices and secondary helical stacking of the nanoflakes. Spin polarisation of the CMNFs was confirmed by chirality-dependent magnetic-tip conducting atomic force microscopy (mc-AFM) and magnetic field-independent magnetic circular dichroism (MCD). Electron transfer in the symmetry-breaking electric field was speculated to create chirality-dependent effective magnetic fields. The asymmetric spin-orbit coupling (SOC) generated by effective magnetic fields selectively modifies the opposite spin motion in the antipodal CMNFs. Our findings provide fundamental insights for directional spin control in unprecedented functional inorganic materials.

Monodisperse nonstoichiometric zinc ferrite nanoparticles with a tunable size of 4.1–32.2 nm are fabricated via thermal decomposition. An extrinsic impurity phase of the ZnO component is present in the zinc ferrite nanoparticles with a size of

In this work, we report the electronic and magnetic properties of epitaxial BiFeO3 (BFO) thin film deposited on SrTiO3 (001) substrate via the chemical solution deposition technique. These properties of pure BFO thin films were characterized by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism techniques (XMCD). The large magnetization at Fe-edge could be due to annealing in nitrogen. Annealing in nitrogen atmosphere increases the grain size and porosity which lead to create more oxygen vacancy. The presence of oxygen vacancies which compensate the bismuth vacancies created due to bismuth volatilization. The origin of large orbital momentum in BFO thin film is also discussed. The O K-edge spectra display large spectral variation depending on the polarization vector E. The structural distortion at oxygen octahedral induces large anisotropy due to Fe 3d–O 2p hybridization. The hybridized Fe 3d orbitals contribute a much larger orbital momentum in BFO thin film.

Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)3]0/+ [10/+; dppf = 1,1'-bis(diphenylphosphino)ferrocene] in two oxidation states by an advanced multitechnique experimental approach. A combination of magnetic circular dichroism, X-ray absorption and emission, high-frequency electron paramagnetic resonance (EPR), and Mossbauer spectroscopies is used to establish that oxidation of 10 occurs on the carbonyl iron ion, resulting in a low-spin iron(I) ion. It is shown that an unequivocal result is obtained by combining several methods. Compound 1+ displays slow spin dynamics, which is used here to study its geometric structure by means of pulsed EPR methods. Surprisingly, these data show an association of the tetrakis[3,5-bis(trifluoromethylphenyl)]borate counterion with 1+.

Single-molecule magnets (SMMs) with d7 electronic configurations often require designer ligands to satisfy the metals electronic conditions to achieve large angular momentum. Herein, the slow relaxation of the magnetization in two d7 metal complexes in near identical ligand fields is achieved from divergent origins. The two compounds, [CoII{N(SiMePh2)2}2] and [K(2,2,2-crypt)][FeI{N(SiMePh2)2}2] (2,2,2-crypt = 2,2,2-cryptand), display unusual electronic configurations giving rise to SMM behavior originating either from 3d–4s orbital mixing or a non-Aufbau ground state. The chracteristics contributing to the rare non-Aufbau ground state configurations are illuminated by the use of a highly donating amido-ligand, which would be expected to significantly split the respective orbitals. Magnetic circular dichroism provides experimental support for ab initio determined electronic structures. Moreover, computational models reveal that the relative electronic configurations are largely retained independently of coordination geometry, provided that some degree of pseudo-linearity is retained. Thus, providing generalized design principles in the pursuit of linear d7 SMMs.

C-term magnetic circular dichroism (MCD) spectroscopy is a powerful method for probing d–d and f–f transitions in paramagnetic metal complexes. However, this technique remains underdeveloped both experimentally and theoretically for studies of U(V) complexes of Oh symmetry, which have been of longstanding interest for probing electronic structure, bonding, and covalency in 5f systems. In this study, C-term NIR MCD of the Laporte forbidden f–f transitions of [UCl6]− and [UF6]− are reported, demonstrating the significant fine structure resolution possible with this technique including for the low energy Γ7 → Γ8 transitions in [UF6]−. The experimental NIR MCD studies were further extended to [U(OC6F5)6]−, [U(CH2SiMe3)6]−, and [U(NC(tBu)(Ph))6]− to evaluate the effects of ligand-type on the f–f MCD fine structure features. Theoretical calculations were conducted to determine the Laporte forbidden f–f transitions and their MCD intensity experimentally observed in the NIR spectra of the U(V) hexahalide complexes, via the inclusion of vibronic coupling, to better understand the underlying spectral fine structure features for these complexes. These spectra and simulations provide an important platform for the application of MCD spectroscopy to this widely studied class of U(V) complexes and identify areas for continued theoretical development.

We report the electronic, magnetic, structural, vibrational, and X-ray absorption spectroscopy of the inverse full-Heusler Fe2IrSi alloy. We employed state-of-the-art first-principles computational techniques. Our ab initio calculations revealed a ferromagnetic half-metallicity with a magnetic moment of ∼5.01 μB, which follows the Slater Pauling rule. We show rich magnetic behavior due to spin–orbit coupling through the entanglement of the Fe-3d/Ir-5d orbitals. The large extension of the Ir-5d orbital and the itinerant Fe-3d states enhanced spin–orbit and electron–electron interactions, respectively. The analyses of our results reveal that electron–electron interactions are essential for the proper description of the electronic properties while spin–orbit coupling effects are vital to accurately characterize the X-ray absorption and X-ray magnetic circular dichroism spectra. We estimate the strength of the spin–orbit coupling by comparing the intensity of the white-line features at the L3 and L2 absorption edges. This led to a branching ratio that deviates strongly from the statistical ratio of 2, indicative of strong spin–orbit coupling effects in the inverse full-Heusler Fe2IrSi alloy.

Novel phenomena and functionalities at interfaces of oxide heterostructures are currently of great interest in a wide range of applications. At such interfaces, charge, spin, orbital and lattice ordering coexist and correlate closely, contributing to rich functional responses. By using atomically resolved imaging and spectroscopy techniques, we investigated magnetic behaviors and structural modulation at the SrFeO3-x/SrTiO3 interface. Fe/Ti element intermixing and oxygen vacancies occurred across a few unit cells at the interface. Furthermore, antiferromagnetic spin ordering of Fe with different valence states in the interface of SrFeO3-x/SrTiO3 induced uncompensated magnetic moments. Compared to the SrFeO3-x/La0.3Sr0.7Al0.65Ta0.35O3 heterojunction, the variations of charge and lattice order parameters at the SrFeO3-x/SrTiO3 interfaces were also determined by advanced electron microscopy, which provided a good understanding of the physical origin of disparate macroscopic magnetic properties, further investigated by magnetometer measurements and X-ray magnetic circular dichroism (XMCD) spectra. These studies provide comprehensive insight into the interfacial modulation of ferrite oxide, which may be useful for designing future devices in oxide electronics.

We proposed a data-driven science study by Bayesian spectroscopy to analyze an X-ray magnetic circular dichroism (XMCD) spectrum and magnetic moments. In Bayesian spectroscopy, model selection beco...

Chiral inorganic nanomaterials have revealed opportunities in various fields owing to their strong light-matter interactions. In particular, chiral metal oxide nanomaterials that can control light and biochemical reactions have been highlighted due to their catalytic activity and biocompatibility. In this study, we present the synthesis of chiral cobalt oxide nanoparticles with a g-factor of 0.01 in the UV-visible region using l- and d-Tyr-Tyr-Cys ligands. The conformation of the Tyr-Tyr-Cys peptide on the nanoparticle surfaces was identified by 2D NMR spectroscopy analysis. In addition, the sequence effect of Tyr-Tyr-Cys developing chiral nanoparticles was analyzed. The revealed peptide structure, along with the experimental results, demonstrate the important role of the thiol group and carboxyl group of the Tyr-Tyr-Cys ligand in chirality evolution. Importantly, due to the magnetic properties of chiral cobalt oxide nanoparticles and their strong absorption in the UV region, the circular dichroism (CD) responses can be dramatically modulated under an external magnetic field.

Giant Zeeman splitting and zero-field splitting (ZFS) are observed in 2D nanosheets that have monolayers of atomic thickness. In this study, single-crystalline CdSe(ethylenediamine)0.5 and Mn2+-doped nanosheets are synthesized via a solvothermal process. Tunable amounts of Mn2+(0.5-8.0%) are introduced, resulting in lattice contraction as well as phosphorescence from five unpaired electrons. The exciton dynamics are dominated by spin-related electronic transitions (4T1 → 6A1) with long lifetimes (20.5, 132, and 295 μs). Temperature-varied EPR spectroscopy with spectral simulation reveals large ZFS (D = 3850 MHz) due to axial distortion of substituted Mn2+ (S = 5/2). In the magnetic circular dichroism (MCD) measurements, we observed giant Zeeman splitting with large effective g values (up to 231 ± 21), which implies huge sp-d exchange interactions in 2D monolayer regimes, leading to diluted magnetic semiconductor (DMS) materials.

Previously, we and other laboratories have reported an unusual and strong Raman optical activity (ROA) induced in solvents by chiral dyes. Various theories of the phenomenon appeared, but they were not capable of explaining fully the observed ROA band signs and intensities. In this work, an analysis based both on the light scattering theory and dedicated experiments provides a more complete understanding. For example, double‐cell magnetic circular dichroism and magnetic ROA experiments with copper‐porphyrin complex show that the induced chirality is observed without any contact of the solvents with the complex. The results thus indicate that a combination of electronic circular dichroism (ECD) with the polarized Raman scattering is responsible for the effect. The degree of circularity of solvent vibrational bands is a principal molecular property participating in the event. The insight and the possibility to predict the chirality transfer promise future applications in spectroscopy, chemical analysis and polarized imaging., In a series of experiments and by a theoretical analysis we decipher Raman optical activity induced in achiral solvents as an interference of two phenomena, circular dichroism and polarized Raman scattering. Applications of this strong effect can be potentially found in analytical chemistry, spectroscopy, and imaging of biologically relevant systems.

High-Frequency and -Field EPR (HFEPR) studies of Fe(TPP)X (X = F, Cl, Br; I, TPP2−= meso-tetraphenylporphyrinate dianion) and far-IR magnetic spectroscopic (FIRMS) studies of Fe(TPP)Br and Fe(TPP)I have been conducted to probe magnetic intra- and inter-Kramers doublet transitions in these S = 5/2 metalloporphyrin complexes, yielding zero-field splitting (ZFS) and g parameters for the complexes: Fe(TPP)F, D = +4.67(1) cm−1, E = 0.00(1) cm−1, g⊥ = 1.97(1), g|| = 2.000(5) by HFEPR; Fe(TPP)Cl, D = +6.458(2) cm−1, E = +0.015(5) cm−1, E/D = 0.002, g⊥ = 2.004(3), g|| = 2.02(1) by HFEPR; Fe(TPP)Br, D = +9.03(5) cm−1, E = +0.047(5) cm−1, E/D = 0.005, giso = 1.99(1) by HFEPR and D = +9.05 cm−1, giso = 2.0 by FIRMS; Fe(TPP)I, D = +13.84 cm−1, E = +0.07 cm−1, E/D = 0.005, giso = 2.0 by HFEPR and D = +13.95 cm−1, giso = 2.0 by FIRMS (the sign of E was in each case arbitrarily assigned as that of D). These results demonstrate the complementary nature of field- and frequency-domain magnetic resonance experiments in extracting with high accuracy and precision spin Hamiltonian parameters of metal complexes with S > 1/2. The spin Hamiltonian parameters obtained from these experiments have been compared with those obtained from other physical methods such as magnetic susceptibility, magnetic Mossbauer spectroscopy, inelastic neutron scattering (INS), and variable-temperature and -field magnetic circular dichroism (VT-VH MCD) experiments. INS, Mossbauer and MCD give good agreement with the results of HFEPR/FIRMS; the others not as much. The electronic structure of Fe(TPP)X (X = F, Cl, Br, I) was studied earlier by multi-reference ab initio methods to explore the origin of the large and positive D-values, reproducing the trends of D from the experiments. In the current work, a simpler model based on Ligand Field Theory (LFT) is used to explain qualitatively the trend of increasing ZFS from X = F to Cl to Br and to I as the axial ligand. Tetragonally elongated high-spin d5 systems such as Fe(TPP)X exhibit D > 0, but X plays a key role. Spin delocalization onto X means that there is a spin–orbit coupling (SOC) contribution to D from X•, as opposed to none from closed-shell X−. Over the range X = F, Cl, Br, I, X• character increases as does the intrinsic SOC of X• so that D increases correspondingly over this range.

In recent years, the importance of analyzing excited triplet states has increased dramatically because of their relevance in the design and development of photofunctional molecules. Since the secon...

Six porphycenes have been synthesized, bearing one, two, or three fluorine atoms attached directly to the 18-π-electron system at the meso positions. These novel compounds have been characterized by structural, electrochemical, and spectral techniques, combined with quantum chemical calculations. In three fluoroporphycenes, the unsymmetric substitution pattern leads to the presence of two nonequivalent trans tautomeric forms. They have been identified using electronic absorption, emission, and magnetic circular dichroism spectroscopies. Their relative energies have been estimated for the ground and lowest excited electronic states. Tautomerization potential is quasi-symmetric in S0 , but becomes strongly nonsymmetric in S1 . Femtosecond transient absorption studies allowed determination of tautomerization rates, larger and similar for both directions of the double hydrogen transfer in S0 , lower and disparate in S1 . Fluoroporphycenes emerge as good candidates for detailed studies of mechanisms of double hydrogen transfer, as well as processes responsible for rapid radiationless excited state depopulation.

Two-dimension (2D) magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing. Their functionality is particularly rich when different magnetic orders are competing in the same material. Metalloxenes REX2 (RE = Eu, Gd; X = Si, Ge), silicene or germanene — heavy counterparts of graphene — coupled with a layer of rare-earth metals, evolve from three-dimension (3D) antiferromagnets in multilayer structures to 2D ferromagnets in a few monolayers. This evolution, however, does not lead to fully saturated 2D ferromagnetism, pointing at a possibility of coexisting/competing magnetic states. Here, REX2 magnetism is explored with element-selective X-ray magnetic circular dichroism (XMCD). The measurements are carried out for GdSi2, EuSi2, GdGe2, and EuGe2 of different thicknesses down to 1 monolayer employing K absorption edges of Si and Ge as well as M and L edges of the rare-earths. They access the magnetic state in REX2 and determine the seat of magnetism, orbital, and spin contributions to the magnetic moment. High-field measurements probe remnants of the bulk antiferromagnetism in 2D REX2. The results provide a new platform for studies of complex magnetic structures in 2D materials.

We investigated the evolution of ferromagnetism in layered Fe3GeTe2 flakes under different pressures and temperatures using in situ magnetic circular dichroism (MCD) spectroscopy. We found that the rectangular shape of the hysteresis loop under an out-of-plane magnetic field sweep can be sustained below 7 GPa. Above that pressure, an intermediate state appears in the low-temperature region signaled by an 8-shaped skewed hysteresis loop. Meanwhile, the coercive field and Curie temperature decrease with increasing pressures, implying the decrease of the exchange interaction and the magneto-crystalline anisotropy under pressures. The intermediate phase has a labyrinthine domain structure, which is attributed to the increase of the ratio of exchange interaction to magneto-crystalline anisotropy based on Jagla's theory. Moreover, our calculations reveal a weak structural transition around 6 GPa that corresponds to a significant change in the FeI-FeI bond length, which has strong influences on magnetic interaction. Detailed analysis on exchange interaction and magneto-crystalline anisotropy with pressure shows a consistent trend with experiments.

X-ray magnetic circular dichroism (XMCD) is a technique commonly used to probe magnetic properties of materials with element and orbital selectivity, which requires the use of circularly polarized (CP) X-rays. It is possible to accomplish XMCD experiments with fixed CP and alternating the magnetic field orientation, but most reliable data are obtained when alternating the magnetization orientation and the polarization between right and left helicities. A versatile strategy has been developed to perform XMCD experiments using a hard X-ray quarter-wave plate, at both polychromatic dispersive and conventional monochromatic optics, in combination with synchronous data acquisition. The switching frequency waveform is fed into a lock-in amplifier to detect and amplify the XMCD signal. The results on a reference sample demonstrate an improvement in data quality and acquisition time. The instrumentation successfully generated 98% of CP X-rays switching the beam helicity at 13 Hz, with the possibility of faster helicity switching once it is installed at the new Brazilian fourth-generation source, SIRIUS.

In the terrestrial dipolar magnetic field, magnetic circular dichroism (MCD) of UV sunlight by paramagnetic O(2) in an Archean atmosphere (mostly CO(2) and N(2)) results in circular polarization anisotropy (~ 10(−10)). This is used to calculate enantiomeric excess (EE~10(−13)) of glyceraldehyde (3-carbon sugar) with a model that includes racemic production and asymmetric photolysis of its enantiomers. The sign and magnitude of enantiomeric excess (EE) vary with the Earth’s latitude. Unlike random noise fluctuation in spontaneous mirror symmetry breaking (SMSB) models, the sign of EE is deterministic and constant over large areas of prebiotic Earth. The magnitude is several orders greater than the mean amplitude of stochastically fluctuating EE. MCD could provide the initial EE for growth of homochirality by asymmetric autocatalysis.

Biogenic nanoscale vanadium magnetite is produced by converting V(V)-bearing ferrihydrites through reductive transformation using the metal-reducing bacterium Geobacter sulfurreducens. With increasing vanadium in the ferrihydrite, the amount of V-doped magnetite produced decreased due to V-toxicity which interrupted the reduction pathway ferrihydrite–magnetite, resulting in siderite or goethite formation. Fe L2,3 and V L2,3 X-ray absorption spectra and data from X-ray magnetic circular dichroism analysis revealed the magnetite to contain the V in the Fe(III) Oh site, predominately as V(III) but always with a component of V(VI), present a consistent V(IV)/V(III) ratio in the range 0.28 to 0.33. The bacteriogenic production of V-doped magnetite nanoparticles from V-doped ferrihydrite is confirmed and the work reveals that microbial reduction of contaminant V(V) to V(III)/V(IV) in the environment will occur below the Fe-redox boundary where it will be immobilised in biomagnetite nanoparticles.

Magnetic circular dichroism (MCD) and absorption spectra of multiferroic HoFe3(BO3)4 of 5I8 → 5F2 and 5F3 f–f transitions are measured at T = 90 K. The absorption spectra are expanded into Lorentzian components, and the transition intensities are obtained. The Zeeman splitting of some transitions is determined using the MCD and absorption spectra. The MCD spectra and Zeeman splitting are theoretically analyzed in the free-atom |J, ±MJ〉 wave function approximation by using the concept of a crystalline quantum number. An inconsistency is revealed when this concept is applied to ions with an integer moment, and a modification of the concept is proposed. Anomalously intense vibronic repetitions of electronic transitions from excited sublevels of the ground multiplet are found.

In this article, intense magneto-optical (MO) activity is demonstrated for plasmonic tungsten oxide WO3–x nanowires/nanorods by magnetic circular dichroism (MCD) spectroscopy. One-dimensional WO3–x...