Magnetic Circular Dichroism Spectra Research Articles

Czochralski Growth, Magnetic Properties and Faraday Characteristics of CeAlO3 Crystals

CeAlO3 crystals were grown in different growth atmospheres by the Czochralski method. The lattice parameters and space group of CeAlO3 crystal were determined by Rietveld structure refinement of X-ray diffraction (XRD) data. The influence of Ce4+ ions in the crystal on the transmittance and crystal color was confirmed by XPS analysis. Magnetization curve at room temperature and temperature dependencies of the magnetic susceptibility in two different directions were measured, indicating that CeAlO3 crystal has remarkable magnetic anisotropy and there is an abnormal magnetic behavior in the vertical <001> direction in the temperature range of 50–150 K. Faraday characteristics of CeAlO3 crystal were investigated at room temperature. Verdet constants of CeAlO3 at 532, 635 and 1064 nm are about 2.1 times as large as those of CeF3. The reason of large Verdet constants was analyzed based on the Van Vleck–Hebb theory and the magnetic circular dichroism (MCD) spectrum.

High-pressure magnetism of the double perovskite Sr2FeOsO6 studied by synchrotron Fe57 Mössbauer spectroscopy

The pressure dependence of the magnetism of the double perovskite ${\mathrm{Sr}}_{2}{\mathrm{FeOsO}}_{6}$ was investigated by temperature- and magnetic-field-dependent synchrotron $^{57}\mathrm{Fe}$ M\ossbauer spectroscopy in the energy domain up to $\ensuremath{\sim}50$ GPa. ${\mathrm{Sr}}_{2}{\mathrm{FeOsO}}_{6}$ is known to feature antiferromagnetic ordering below ${T}_{\mathrm{N}}\ensuremath{\sim}140$ K and a change in spin structure from AF1 to AF2 near 70 K at ambient pressure. Previous Os ${L}_{2,3}$ x-ray magnetic circular dichroism (XMCD) spectra [Veiga et al., Phys. Rev. B 91, 235135 (2015)] indicated a pressure-driven change from the antiferromagnetic to the ferrimagnetic state. Raman spectra of ${\mathrm{Sr}}_{2}{\mathrm{FeOsO}}_{6}$ collected at room temperature and up to 34 GPa are in agreement with previous x-ray-diffraction studies which verified that the tetragonal ambient pressure crystal structure is retained at high pressure. The M\ossbauer investigations show that the Fe ions remain in the +3 high-spin $({{t}_{2g}}^{3}{e}_{g}^{2})$ state over the whole pressure range. The magnetic ordering is strongly stabilized by high pressure and for $pg30$ GPa the ordering temperature is increased to above room temperature. Broad magnetic hyperfine patterns as well as coexistence of magnetic and paramagnetic signals at high pressures indicate the formation of inhomogeneous magnetic states. The shapes of applied-field M\ossbauer spectra at low temperature are similar at 2 and 33 GPa and do not allow resolution of distinct antiferromagnetic and ferrimagnetic components. Pressure-induced spin canting in a basically antiferromagnetic spin structure or magnetic phase separation involving a pressure-induced minority ferrimagnetic phase may be the origin for the ferromagnetic XMCD signal.

An ab Initio Linear Response Method for Computing Magnetic Circular Dichroism Spectra with Nonperturbative Treatment of Magnetic Field.

Magnetic circular dichroism (MCD) experiments provide a sensitive tool for exploring geometric, magnetic, and electronic properties of chemical complexes and condensed matter systems. They are also challenging to simulate because of the need to simultaneously treat the perturbations of a finite magnetic field as well as an optical field. In this work, we introduce an ab initio approach that treats the external magnetic field nonperturbatively with London orbitals for simulating the MCD spectra of closed-shell systems. Effects of a magnetic field are included variationally in the spin-free nonrelativistic Hamiltonian, followed by a linear response formalism to directly calculate the difference in absorption between the left and right circularly polarized light. In addition to the presentation of underlying mathematical formalism and implementation, the method developed in this paper has been applied to simulations of MCD spectra of the sodium anion, 2,2,6,6-tetramethylcyclohexanone, and 3-methyl-2-hexanone. Results are discussed and compared to experiments.

Magnetic circular dichroism and absorption spectra of [formula omitted] transition in HoAl3(BO3)4 and HoFe3(BO3)4 single crystals

Comparative study of magnetic circular dichroism (MCD) and absorption spectra of HoAl3(BO3)4 and HoFe3(BO3)4 single crystals in the region of I85→F55 transition of the Ho3+ ion was carried out. Absorption spectra were decomposed into the Lorentz shape components and intensities of transitions were obtained. Unusually strong vibronic transitions were observed in HoAl3(BO3)4, but were not observed in HoFe3(BO3)4 that testified to the strong non diagonal vibronic interaction in HoAl3(BO3)4. The MCD spectra were analyzed in approximation of the |J,±MJ〉 wave functions of the free atom and using concept of the crystal quantum number. Peculiarity of application of this concept to ions with integer moments was revealed and modification of the concept was suggested. With the help of the MCD spectra, the Zeeman splitting of some transitions was found. In particular, the Landé factor gC≈2 of the ground state of the Ho3+ ion in HoAl3(BO3)4 in the trigonal axis direction was determined. It appeared to be five times less than that in HoFe3(BO3)4 also found with the help of the MCD.

Atomistic Defect Makes a Phase Plate for the Generation and High-Angular Splitting of Electron Vortex Beams.

Topological defects in solid-state materials by breaking the translational symmetry offer emerging properties that are not present in their parental phases. For example, edge dislocations-the 2π phase-winding topological defects-in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to topological orders when they interact with a high-energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, we found the amplitude patterns of the ⟨020⟩ Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. Technologically, this approach provides a feasible route for the fabrication of phase plates that can generate electron vortex beams with an angular separation that is 3 orders of magnitude larger than what traditional nanofabrication technology can offer. This advance will enable the collection of magnetic circular dichroism spectra with high spatial resolution and high efficiency, boosting the understanding of the relationship between symmetry breaking and magnetic property of individual topological defect at the atomic scale.

Magneto-optical spectra and the presence of an impurity band in p-type ferromagnetic semiconductor (Ga,Fe)Sb with high Curie temperature

By using magnetic circular dichroism (MCD) spectroscopy with photon energy in both visible (1.5–5 eV) and infrared light regions (0.6–1.7 eV), we systematically investigate the band structure of p-type ferromagnetic semiconductor (Ga1−x,Fex)Sb with various Fe concentrations x = 2%–20% grown by low-temperature molecular beam epitaxy. We observed two peaks in the infrared MCD spectra that can be explained by the optical transitions related to the Fermi level (EF) located in an Fe-related impurity band (IB) in the bandgap. As x increases, the energy shifts of the two peaks suggest that the Fe-related IB extends into the bandgap and EF rises correspondingly. Furthermore, the mobility of hole carriers in these (Ga,Fe)Sb thin films estimated by Hall measurements is very low (0.2–2 cm2/Vs), which is consistent with our conclusion that the hole carriers and EF reside in the IB rather than in the valence band. Our results provide insights into the band structure of p-type ferromagnetic semiconductors (Ga,Fe)Sb with high Curie temperature, which is promising for the realization of spintronic devices operating at room temperature.

Effect of gadolinium on magnetic circular dichroism and electron magnetic resonance of ε-Fe2O3 nanoparticles formed in borate glasses

A remarkable characteristic of borate glasses is the ability of forming magnetic nanoparticles at low doping with transition element oxides. We have studied structure and magnetic properties of iron oxide nanoparticles formed in borate glasses, in particular, concentration and temperature dependences of magnetic circular dichroism (MCD) and electron magnetic resonance (EMR) spectra. A series of glasses of molar composition 22.5K2O-22.5Al2O3–55B2O3 doped with 1.5 mass % of Fe2O3 and different contents of Gd2O3 from 0.1 to 1.0 mass % was prepared using a conventional melt quenching technique and subjected to an additional thermal treatment. The whole set of results allows to identify the predominant magnetic phase in these glasses as ε-Fe2O3 nanoparticles, with a considerable part of iron ions substituted by gadolinium. Analysis and computer simulations of the EMR spectra allow separating the contribution of electron paramagnetic resonance of diluted iron ions and together with the temperature dependences of magnetization demonstrate a superparamagnetic character of the nanoparticle magnetism.

Electronic structure and exciton shifts in Sb-doped MoS2 monolayer

The effective manipulation of excitons is important for the realization of exciton-based devices and circuits, and doping is considered a good strategy to achieve this. While studies have shown that 2D semiconductors are ideal for excitonic devices, preparation of homogenous substitutional foreign-atom-doped 2D crystals is still difficult. Here we report the preparation of homogenous monolayer Sb-doped MoS2 single crystals via a facile chemical vapor deposition method. A and B excitons are observed in the Sb-doped MoS2 monolayer by reflection magnetic circular dichroism spectrum measurements. More important, compared with monolayer MoS2, the peak positions of two excitons show obvious shifts. Meanwhile, the degeneration of A exciton is also observed in the monolayer Sb-doped MoS2 crystal using photoluminescence spectroscopy, which is ascribed to the impurity energy levels within the band-gap, confirmed by density function theory. Our study opens a door to developing the doping of 2D layered transition metal dichalcogenides with group-V dopants, which is helpful for the fundamental study of the physical and chemical properties of transition metal dichalcogenides.

Magnetic circular dichroism spectra of transition metal complexes calculated from restricted active space wavefunctions.

First principles multiconfigurational restricted active space (RAS) self-consistent field (SCF) or configuration interaction (CI) approaches, augmented with a treatment of spin-orbit coupling by state interaction, were used to calculate the magnetic circular dichroism (MCD) , , and/or for closed- and open-shell transition metal complexes: PdCl42-, PdBr42-, AuCl4-, AuBr4-, MnO4-, CuCl42-, CuBr42-, and Fe(CN)63-. The were determined with a sum-over-states approach. It is shown that reasonably accurate MCD spectra can be obtained directly at a RAS level or at a RAS level augmented with corrections for the dynamic correlation. The sign and magnitude of the individual MCD terms can be unambiguously determined and assigned to particular electronic transitions.

Correlation between magneto-optical and transport properties of Sr doped manganite films

The features of electronic structure of La0.7Sr0.3MnO3, Pr0.8Sr0.2MnO3, and Pr0.6Sr0.4MnO3 polycrystalline films of different thickness have been investigated using magnetic circular dichroism (MCD) in the range of 1.1–4.2 eV. The temperature behavior of the samples electrical resistance were also has been studied. It was found that films with high Sr content (0.3 and 0.4) act as high-temperature semiconductors, while the maximum in the temperature dependences of resistivity these films indicates the transition of the samples to the metallic state at some temperature TM-S, which is different for different sample thickness. The films with the lower Sr content (0.2) act as insulators in the used temperature range. The MCD spectra have been decomposed to the Gaussian-shaped lines, and the temperature dependence of intensity of each line has been analyzed in comparison with temperature dependence of the films magnetization and with their electric conductivity type. Different temperature behavior of the intensity of four specified Gaussian-lines was revealed for semiconductor films. In the case of insulating Pr0.8Sr0.2MnO3 samples, the intensity of three specified Gaussian lines changes with the temperature in the same way as the magnetization changed. It was established that the lanthanide (La, Pr) type does not affect the MCD spectra shape for the films with the same electrical conductivity type. Besides, the correlation between the MCD data of the films and their conductivity type was revealed. Due to the detailed analysis of the specified Gaussian lines with taking into account the well-known in the literature absorption bands, lying outside the studied spectral region, the MCD bands for the studied manganite films have been identified with electronic transitions of a different nature.

Differential quenching of the angular momentum of the B and Q bands of a porphyrin as a result of extended ring π-conjugation

A novel porphyrin, whose [Formula: see text]-system has been extended via the presence of two additional carbon–carbon triple bonds on opposite meso-positions and by fusion of a single naphthalene unit simultaneously bridging the third meso-position and the [Formula: see text]-carbon of one of the pyrroles, has been synthesized in good yield. Absorption, magnetic circular dichroism, emission, and theoretical spectra are reported for the fused and unfused trans-naphthalene free base and zinc porphyrins. The fusing of one of the naphthalene moieties results in significant changes to the absorption spectrum and, very unusually, the bridged meso-[Formula: see text]-pyrrole fusion results in quenching of the MCD Faraday pseudo-A term in the porphyrin’s B band (S2). This unique effect was interpreted as resulting from the origin of the electronic structure of the second excited state (the B state). The [Formula: see text] and [Formula: see text] polarizations are completely mixed by the electronic effects of the non-symmetric extended conjugation of the [Formula: see text] ring. Analysis of the origin of the MCD signal indicates that the presence of this novel mixed polarization leads to negligible angular momentum in the important B state. To our knowledge, this is the first report in which the magnetic moment in a porphyrin’s intensely absorbing B band has been quenched while the angular momentum in the Q band, the first excited state, remains as normal. This implies that the photophysical properties of the B state are likely very different than those of the Q state, which has novel and significant implications for applications, especially in non-linear spectroscopy.

UV Absorption and Magnetic Circular Dichroism Spectra of Purine, Adenine, and Guanine: A Coupled Cluster Study in Vacuo and in Aqueous Solution.

The absorption and magnetic circular dichroism (MCD) spectra of purine and of the purine nucleobases adenine and guanine have been calculated in gas phase at the Coupled Cluster Singles and Doubles (CCSD) and Resolution-of-Identity Singles and Approximate Doubles (RI-CC2) levels of theory. Exploiting a new development in the TURBOMOLE program package for computing vertical excitation energies and Faraday [Formula: see text] terms in an implicit solvent approximated by the conductor-like screening model (COSMO) at the CC2 level, we have investigated the solvent effects on the relative positions of the ππ* and nπ* electronic transitions in these three molecules and compared them to the corresponding vacuum results. In the case of adenine, we also included specific solvent effects with a small water cluster. The spectra obtained with the implicit model COSMO are in qualitative agreement with those obtained with explicit water molecules both with and without the inclusion of the bulk solvent effects via the continuum solvent model. This suggests that the inclusion of the electrostatic contributions of the solvent can provide a sufficiently accurate description of the absorption spectra for adenine. The results for purine, adenine, and guanine show that, after the inclusion of bulk solvation, the ππ* states shift to lower energies while at the same time nπ* states show a reversed behavior. The computed MCD spectra show the characteristic bisignate profile found experimentally in all cases, despite, for adenine, remarkable differences in the origin of the individual peaks for different computational methods. Therefore, the ability (or inability) of MCD to determine the relative stability of the La and Lb states is critically reassessed. According to our best estimate for adenine in aqueous solution, the La state is more stable than Lb.

Modeling of Magnetic Circular Dichroism and UV/Vis Absorption Spectra Using Fluctuating Charges or Polarizable Embedding within a Resonant-Convergent Response Theory Formalism.

In recent years computational methods based on embedding have become of increasing popularity when the aim is to introduce environmental effects into quantum chemistry calculations of molecular properties. This is due in particular to the efficiency of such methods while still retaining a high degree of accuracy compared to full quantum chemistry treatments. In the present paper we compare two popular embedding methods-fluctuating charges (FQ) and polarizable embedding (PE)-highlighting their similar mathematical structure. Furthermore, based on a unified formulation of the two embedding methods, we present theory and implementation of these embedding methods within resonant-convergent response theory up to the level of quadratic response. A numerical comparison between FQ and PE is presented for a set of solute-solvent systems based on calculations of UV/vis and magnetic circular dichroism spectra. Overall, we find in the cases considered the FQ and PE models to perform rather similarly, especially upon introducing effects of explicit conformational sampling into the theoretical predictions.

Magnetic Circular Dichroism in 2D Colloidal Semiconductor Nanocrystals

Magnetic circular dichroism (MCD) spectra were measured for colloidal CdSe/CdS core–wing nanoplatelets (NPLs). MCD spectra of CdSe cores demonstrate well resolved features which could be attributed to excitonic transitions from heavy hole, light hole and split-off sublevels. A1/D0, B0/D0 MCD characteristic terms were determined. The values of A1/D0, B0/D0 terms have no dependence on NPL thickness and are very close to the corresponding values in organic molecules.

Cation distribution and magnetic properties in ultrathin(Ni1–xCox)Fe2O4(x=0–1)layers on Si(111) studied by soft x-ray magnetic circular dichroism

We study the electronic structure and the magnetic properties of epitaxial (Ni1-xCox)Fe2O4(111) layers (x = 0 - 1) with thicknesses d = 1.7 - 5.2 nm grown on Al2O3(111)/Si(111) structures, to achieve a high value of inversion parameter y, which is the inverse-to-normal spinel-structure ratio, and hence to obtain good magnetic properties even when the thickness is thin enough for electron tunneling as a spin filter. We revealed the crystallographic (octahedral Oh or tetrahedral Td) sites and the valences of the Fe, Co, and Ni cations using experimental soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism spectra and configuration-interaction cluster-model calculation. In all the (Ni1-xCox)Fe2O4 layers with d = about 4 nm, all Ni cations occupy the Ni2+ (Oh) site, whereas Co cations occupy the three different Co2+ (Oh), Co2+ (Td), and Co3+ (Oh) sites with constant occupancies. According to these features, the occupancy of the Fe3+ (Oh) cations decreases and that of the Fe3+ (Td) cations increases with decreasing x. Consequently, we obtained a systematic increase of y with decreasing x and achieved the highest y value of 0.91 for the NiFe2O4 layer with d = 3.5 nm. From the d dependences of y and magnetization in the d range of 1.7 - 5.2 nm, a magnetically dead layer is present near the NiFe2O4/Al2O3 interface, but its influence on the magnetization was significantly suppressed compared with the case of CoFe2O4 layers reported previously [Y. K. Wakabayasi et al., Phys. Rev. B 96, 104410 (2017)], due to the high site selectivity of the Ni cations. Since our epitaxial NiFe2O4 layer with d = 3.5 nm has a high y values (0.91) and a reasonably large magnetization (180 emu/cc), it is expected to exhibit a strong spin filter effect, which can be used for efficient spin injection into Si.

Anisotropy in the magnetic interaction and lattice-orbital coupling of single crystal Ni3TeO6

This investigation reports on anisotropy in the magnetic interaction, lattice-orbital coupling and degree of phonon softening in single crystal Ni3TeO6 (NTO) using temperature- and polarization-dependent X-ray absorption spectroscopic techniques. The magnetic field-cooled and zero-field-cooled measurements and temperature-dependent Ni L3,2-edge X-ray magnetic circular dichroism spectra of NTO reveal a weak Ni-Ni ferromagnetic interaction close to ~60 K (TSO: temperature of the onset of spin ordering) with a net alignment of Ni spins (the uncompensated components of the Ni moments) along the crystallographic c-axis, which is absent from the ab-plane. Below the Néel temperature, TN~ 52 K, NTO is stable in the antiferromagnetic state with its spin axis parallel to the c-axis. The Ni L3,2-edge X-ray linear dichroism results indicate that above TSO, the Ni 3d eg electrons preferentially occupy the out-of-plane 3d3z2−r2 orbitals and switch to the in-plane 3dx2−y2 orbitals below TSO. The inherent distortion of the NiO6 octahedra and anisotropic nearest-neighbor Ni-O bond lengths between the c-axis and the ab-plane of NTO, followed by anomalous Debye-Waller factors and orbital-lattice in conjunction with spin-phonon couplings, stabilize the occupied out-of-plane (3d3z2−r2) and in-plane (3dx2−y2) Ni eg orbitals above and below TSO, respectively.

Syntheses and crystal structures of neodymium(III) and europium(III) complexes bearing dimethyl-, pyrrolidine-, or S-prolinol- dithiocarbamato ligands and their natural and magnetic circular dichroism spectra

A series of NdIII and EuIII complexes containing achiral or chiral dithiocarbamato (dtc) ligands, [Ln(Xdtc)3(NN)] {Ln = Nd or Eu; X = dimethyl- (Me2), pyrrolidine- (pyr), or (S)-prolinol- (S-proOH); NN = 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy)}, were prepared and their crystal structures and spectroscopic properties, in particular the natural circular dichroism (CD) and magnetic circular dichroism (MCD), were investigated. The crystal structures of the complexes analyzed by the X-ray diffraction method showed an 8-coordinate geometry around the LnIII center with comparable structural parameters to one another and to the related complexes reported previously. These complexes exhibited similar spectral patterns in their absorption, natural CD and MCD spectra in solution. Weak but characteristic sharp f–f transition bands were observed in the absorption and MCD spectra, but no CD signals associated with these transitions were observed even in the S-proOHdtc complexes. The MCD spectral pattern of the EuIII complexes revealed a local C2v symmetry around the LnIII center in solution, in contrast to the aqua and the analogous β-diketonato EuIII complexes.

Deterministic, Reversible, and Nonvolatile Low-Voltage Writing of Magnetic Domains in Epitaxial BaTiO3/Fe3O4 Heterostructure.

The ability to electrically write magnetic bits is highly desirable for future magnetic memories and spintronic devices, though fully deterministic, reversible, and nonvolatile switching of magnetic moments by electric field remains elusive despite extensive research. In this work, we develop a concept to electrically switch magnetization via polarization modulated oxygen vacancies, and we demonstrate the idea in a multiferroic epitaxial heterostructure of BaTiO3/Fe3O4 fabricated by pulsed laser deposition. The piezoelectricity and ferroelectricity of BaTiO3 have been confirmed by macro- and microscale measurements, for which Fe3O4 serves as the top electrode for switching the polarization. X-ray absorption spectroscopy and X-ray magnetic circular dichroism spectra indicate a mixture of Fe2+ and Fe3+ at O h sites and Fe3+ at T d sites in Fe3O4, while the room-temperature magnetic domains of Fe3O4 are revealed by microscopic magnetic force microscopy measurements. It is demonstrated that the magnetic domains of Fe3O4 can be switched by not only magnetic fields but also electric fields in a deterministic, reversible, and nonvolatile manner, wherein polarization reversal by electric field modulates the oxygen vacancy distribution in Fe3O4, and thus its magnetic state, making it attractive for electrically written magnetic memories.

Giant magneto-optical Faraday effect of graphene on Co in the soft x-ray range

Using polarization analysis of linearly polarized synchrotron radiation we demonstrate the existence of a giant magneto-optical Faraday effect at the carbon $1s$ edge of single-layer graphene on Co, reaching Faraday rotation angles of $2.9\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.16em}{0ex}}\mathrm{deg}/\mathrm{mm}$. This value is of the order of those observed at the Co $3p$ and $2p$ edges. Using element-selective magnetic hysteresis curves we find that graphene on Co exhibits ferromagnetic order. The magnetism in graphene is found to be carried by and be strongly enhanced by aligned \ensuremath{\pi} orbitals of carbon atoms. It is induced by hybridization with the Co $3{d}_{z}2$ orbitals while carbon \ensuremath{\sigma} bonds show negligible magnetism due to insignificant hybridization with Co. From additional x-ray magnetic circular dichroism and transversal magneto-optical Kerr effect spectra a magnetic moment of $0.14\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$ is estimated for graphene. From Faraday spectra the complete set of x-ray magneto-optical constants of graphene has been deduced which allows for future modeling of magneto-optical devices based on graphene. The strong magnetism in graphene results from hybridization of carbon ${p}_{\mathrm{z}}$ and metal $3d$ orbitals. Atoms of the graphene sublattice A, placed on top of Co, lead to strongest hybridization with Co $3{{d}_{z}}^{2}$ orbitals. Carbon atoms of sublattice B, and those of rotated graphene domains without Co atoms beneath, hybridize with each other and with $3{d}_{\mathrm{xz}}$ and $3{d}_{\mathrm{yz}}$ orbitals of neighboring Co atoms forming tilted ${p}_{\mathrm{z}}$ bonds. We show that the related reduction of A-B symmetry leads to a splitting of the spin-polarized density of conduction-band states which is responsible for the strong magneto-optical Faraday effect.

Magnetic X-ray spectroscopy of two-dimensional CrI3 layers

The recently confirmed monolayer ferromagnet CrI3 is a frisky example of a two-dimensional ferromagnetic material with great application potential in van der Waals heterostructures. Here we present a soft X-ray absorption spectroscopy study of the magnetic bulk properties of CrI3, giving insight into the magnetic coupling scenario which is relevant for understanding its thickness-dependent magnetic properties. The experimental Cr L2,3 X-ray magnetic circular dichroism spectra show a good agreement with calculated spectra for a hybridized ground state. In this high-spin Cr ground state the Cr–I bonds show a strongly covalent character. This is responsible for the strong superexchange interaction and increased spin-orbit coupling, resulting in the large magnetic anisotropy of the two-dimensionally layered CrI3 crystal.