Spin Ground State Research Articles

CaMn3IV O4 Cubane Models of the Oxygen-Evolving Complex: Spin Ground States S

We report the single crystal XRD and MicroED structure, magnetic susceptibility, and EPR data of a series of CaMn3IV O4 and YMn3IV O4 complexes as structural and spectroscopic models of the cuboidal subunit of the oxygen-evolving complex (OEC). The effect of changes in heterometal identity, cluster geometry, and bridging oxo protonation on the spin-state structure was investigated. In contrast to previous computational models, we show that the spin ground state of CaMn3IV O4 complexes and variants with protonated oxo moieties need not be S=9/2. Desymmetrization of the pseudo-C3 -symmetric Ca(Y)Mn3IV O4 core leads to a lower S=5/2 spin ground state. The magnitude of the magnetic exchange coupling is attenuated upon oxo protonation, and an S=3/2 spin ground state is observed in CaMn3IV O3 (OH). Our studies complement the observation that the interconversion between the low-spin and high-spin forms of the S2 state is pH-dependent, suggesting that the (de)protonation of bridging or terminal oxygen atoms in the OEC may be connected to spin-state changes.

Structurally Characterized μ-1,2-Peroxo/Superoxo Dicopper(II) Pair.

Superoxo complexes of copper are primary adducts in several O2-activating Cu-containing metalloenzymes as well as in other Cu-mediated oxidation and oxygenation reactions. Because of their intrinsically high reactivity, however, isolation of Cux(O2•-) species is challenging. Recent work (J. Am. Chem. Soc. 2017, 139, 9831; 2019, 141, 12682) established fundamental thermochemical data for the H atom abstraction reactivity of dicopper(II) superoxo complexes, but structural characterization of these important intermediates was so far lacking. Here we report the first crystallographic structure determination of a superoxo dicopper(II) species (3) together with the structure of its 1e- reduced peroxo congener (2; a rare cis-μ-1,2-peroxo dicopper(II) complex). Interconversion of 2 and 3 occurs at low potential (-0.58 V vs Fc/Fc+) and is reversible both chemically and electrochemically. Comparison of metric parameters (d(O-O) = 1.441(2) Å for 2 vs 1.329(7) Å for 3) and of spectroscopic signatures (ν̃(16O-16O) = 793 cm-1 for 2 vs 1073 cm-1 for 3) reflects that the redox process occurs at the bridging O2-derived unit. The CuII-O2•--CuII complex has an S = 1/2 spin ground state according to magnetic and EPR data, in agreement with density functional theory calculations. Computations further show that the potential associated with changes of the Cu-O-O-Cu dihedral angle is shallow for both 2 and 3. These findings provide a structural basis for the low reorganization energy of the kinetically facile 1e- interconversion of μ-1,2-superoxo/peroxo dicopper(II) couples, and they open the door for comprehensive studies of these key intermediates in Cux/O2 chemistry.

Nuclear Spin Squeezing in Helium-3 by Continuous Quantum Nondemolition Measurement.

We propose a technique to control the macroscopic collective nuclear spin of a helium-3 gas in the quantum regime using light. The scheme relies on metastability exchange collisions to mediate interactions between optically accessible metastable states and the ground-state nuclear spin, giving rise to an effective nuclear spin-light quantum nondemolition interaction of the Faraday form. Our technique enables measurement-based quantum control of nuclear spins, such as the preparation of spin-squeezed states. This, combined with the day-long coherence time of nuclear spin states in helium-3, opens the possibility for a number of applications in quantum technology.

Accurate simulation for finite projected entangled pair states in two dimensions

Based on the scheme of variational Monte Carlo sampling, we develop an accurate and efficient two-dimensional tensor-network algorithm to simulate quantum lattice models. We find that Monte Carlo sampling shows huge advantages in dealing with finite projected entangled pair states, which allows significantly enlarged system size and improves the accuracy of tensor network simulation. We demonstrate our method on the square-lattice antiferromagnetic Heisenberg model up to $32 \times 32$ sites, as well as a highly frustrated $J_1-J_2$ model up to $24\times 24$ sites. The results, including ground state energy and spin correlations, are in excellent agreement with those of the available quantum Monte Carlo or density matrix renormalization group methods. Therefore, our method substantially advances the calculation of 2D tensor networks for finite systems, and potentially opens a new door towards resolving many challenging strongly correlated quantum many-body problems.

Hyperfine and nuclear quadrupole splitting of the NV− ground state in 4H -SiC

Optically addressable spin-triplet defects in silicon carbide, such as divacancies and negatively charged nitrogen vacancy $({\mathrm{NV}}^{\ensuremath{-}})$ allow to develop modern quantum technologies operating in the near-infrared range based on the well-developed semiconductor material. Here, by means of both high-frequency (94 GHz) pulsed electron paramagnetic resonance (EPR) and electron-nuclear double Rresonance (ENDOR) techniques the ground state properties of the negatively charged ${\mathrm{NV}}^{\ensuremath{-}}$ defect in $4H$-SiC were studied. We experimentally determined the ordering of the ground state spin sublevels and established the sign of the zero-field splitting to be positive as predicted by theory. Analysis of nuclear magnetic resonance transitions in ENDOR spectra allowed to determine the sign, symmetry, and absolute values of the hyperfine interaction of the ${\mathrm{NV}}^{\ensuremath{-}}$ defect electron spin with $^{14}\mathrm{N}$ nuclear spin as ${\mathit{A}}_{\ensuremath{\parallel}}=\ensuremath{-}1.142\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$ and ${\mathit{A}}_{\ensuremath{\perp}}=\ensuremath{-}1.184\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$. The absolute value of the nuclear quadrupole interaction constant reflecting an interaction between the $^{14}\mathrm{N}$ nuclear electric quadrupole moment with the electric field gradient was determined to be $|{\mathit{C}}_{q}|=2.44\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$. This large value is compatible with a threefold coordinated $^{14}\mathrm{N}$ nucleus with uniaxial symmetry and proves conclusively the existence of a nearestneighbor ${\mathrm{N}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ pair in the material. For this ${\mathrm{NV}}^{\ensuremath{-}}$ defect, an ensemble (Hahn-echo) coherence time of ${\mathit{T}}_{\text{2}}=49\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ was measured, a value which is in the range previously reported for silicon vacancy spin ensembles and slightly longer than ${\mathit{T}}_{\text{2}}=40\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ measured here on the divacancy spin ensemble.

Reductive Hydrogenation under Single-Site Control: Generation and Reactivity of a Transient NHC-Stabilized Tantalum(III) Alkoxide.

One of the most attractive routes for the preparation of reactive tantalum(III) species relies on the efficient salt-free hydrogenolysis of tantalum(V) alkyls or tantalum(V) alkylidenes, a process known as reductive hydrogenation. For silica-crafted tantalum alkyls and alkylidenes, this process necessarily proceeds at well-separated tantalum centers, while related reductive hydrogenations in homogeneous solution commonly involve dimeric complexes. Herein, an NHC scaffold was coordinated to a novel tri(alkoxido)tantalum(V) alkylidene to circumvent the formation of dimers during reductive hydrogenation. Employing this new model system, a key intermediate of the process, namely a hydrido-tantalum alkyl, was isolated for the first time and shown to exhibit a bidirectional reactivity. Upon being heated, the latter complex was found to undergo either an α-elimination or a reductive alkane elimination. In the (overall unproductive) α-elimination step, H2 and the parent alkylidene were regenerated, while the sought-after transient d2-configured tantalum(III) derivative was produced along the reaction coordinate of the reductive alkane elimination. The reactive low-valence metal center was found to rapidly attack one of the NHC substituents via an oxidative C-H activation, which led to the formation of a cyclometalated tantalum(V) hydride. The proposed elemental steps are in line with kinetic data, deuterium labeling experiments, and density functional theory (DFT) modeling studies. DFT calculations also indicated that the S = 0 spin ground state of the Ta(III) center plays a crucial role in the cyclometalation reaction. The cyclometalated Ta(V) hydride was further investigated and reacted with several alkenes and alkynes. In addition to a rich insertion and isomerization chemistry, these studies also revealed that the former hydride may undergo a formal cycloreversion and thus serve as a tantalum(III) synthon, although the original tantalum(III) intermediate is not involved in this process. The latter reactivity was observed upon reaction with internal alkynes and led to the corresponding η2-alkyne derivatives via vinyl intermediates, which rearrange via a remarkable, hitherto unprecedented, hydrogen shift reaction.

Revisiting the Electronic Structure of Cobalt Porphyrin Nitrene and Carbene Radicals with NEVPT2-CASSCF Calculations: Doublet versus Quartet Ground States.

Cobalt porphyrin complexes are established catalysts for carbene and nitrene radical group-transfer reactions. The key carbene and mono- and bisnitrene radical complexes coordinated to [Co(TPP)] (TPP = tetraphenylporphyrin) have previously been investigated with a variety of experimental techniques and supporting (single-reference) density functional theory (DFT) calculations that indicated doublet (S = 1/2) ground states for all three species. In this contribution, we revisit their electronic structures with multireference N-electron valence state perturbation theory (NEVPT2)-complete-active-space self-consistent-field (CASSCF) calculations to investigate possible multireference contributions to the ground-state wave functions. The carbene ([CoIII(TPP)(•CHCO2Et)]) and mononitrene ([CoIII(TPP)(•NNs)]) radical complexes were confirmed to have uncomplicated doublet ground states, although a higher carbene or nitrene radical character and a lower Co–C/N bond order was found in the NEVPT2-CASSCF calculations. Supported by electron paramagnetic resonance analysis and spin counting, paramagnetic molar susceptibility determination, and NEVPT2-CASSCF calculations, we report that the cobalt porphyrin bisnitrene complex ([CoIII(TPP•)(•NNs)2]) has a quartet (S = 3/2) spin ground state, with a thermally accesible multireference and multideterminant “broken-symmetry” doublet spin excited state. A spin flip on the porphyrin-centered unpaired electron allows for interconversion between the quartet and broken-symmetry doublet spin states, with an approximate 10-fold higher Boltzmann population of the quartet at room temperature.

Synthesis, structure, and C–H bond activation reaction of an iron(IV) terminal imido complex bearing trifluoromethyl groups

Iron terminal imido species featuring electron-withdrawing N-substituents represent an important category of reactive metal-ligand-multiple-bond intermediates in iron-catalyzed reactions. Knowledge of them is very limited, however, as isolable complexes of this type are hard to access. Here, we report an isolable iron(IV) imido complex with trifluoromethyl on nitrogen, namely [(IPr)Fe(NC(CF3)2Ph)2]. We prepared the complex from the reaction of a low-coordinate iron(0) complex with N3C(CF3)2Ph. It has an S = 1 ground spin-state, long Fe-N(imido) bonds, and bent Fe-N(imido)-C(imido) alignments and can undergo intramolecular C–H bond activation reaction to transform into an iron(II) amido complex. Theoretical study suggests that the C–H bond activation reaction involves hydrogen-atom-abstraction mechanism and that the electron-withdrawing nature of trifluoromethyl group renders the imido ligands in [(IPr)Fe(NC(CF3)2Ph)2] and the transition state of the hydrogen-atom-abstraction step structurally close to each other, resulting in a low activation barrier.

Topology and ground state control in open-shell donor-acceptor conjugated polymers

Donor-acceptor (DA) conjugated polymers (CPs) with narrow bandgaps and open-shell (diradical) character represent an emerging class of materials whose rich behavior emanates from their collective electronic properties and diminished electron pairing. However, the structural and electronic heterogeneities that define these materials complicate bandgap control at low energies and connections linking topology, exchange interactions, and (opto)electronic functionality remain nascent. To address these challenges, we demonstrate structurally rigid and strongly π-conjugated copolymers comprised of a solubilizing thiadiazoloquinoxaline acceptor and cyclopenta[2,1-b:3,4-b′]dithiophene or dithieno[3,2-b:2′,3′-d]thiophene donors. Atom-specific substitution modulates local aromatic character within the donor resulting in dramatic differences in structural, physicochemical, electronic, and magnetic properties of the polymers. These long-range π-mediated interactions facilitate control between low-spin aromatic and high-spin quinoidal forms. This work provides a strategy to understand the evolution of the electronic structure within DA CPs, control the ground state spin multiplicity, tune spin-spin interactions, and articulate the emergence of their novel properties.

Creation of Negatively Charged Boron Vacancies in Hexagonal Boron Nitride Crystal by Electron Irradiation and Mechanism of Inhomogeneous Broadening of Boron Vacancy-Related Spin Resonance Lines.

Optically addressable high-spin states (S ≥ 1) of defects in semiconductors are the basis for the development of solid-state quantum technologies. Recently, one such defect has been found in hexagonal boron nitride (hBN) and identified as a negatively charged boron vacancy (). To explore and utilize the properties of this defect, one needs to design a robust way for its creation in an hBN crystal. We investigate the possibility of creating centers in an hBN single crystal by means of irradiation with a high-energy (E = 2 MeV) electron flux. Optical excitation of the irradiated sample induces fluorescence in the near-infrared range together with the electron spin resonance (ESR) spectrum of the triplet centers with a zero-field splitting value of D = 3.6 GHz, manifesting an optically induced population inversion of the ground state spin sublevels. These observations are the signatures of the centers and demonstrate that electron irradiation can be reliably used to create these centers in hBN. Exploration of the spin resonance line shape allowed us to establish the source of the line broadening, which occurs due to the slight deviation in orientation of the two-dimensional B-N atomic plains being exactly parallel relative to each other. The results of the analysis of the broadening mechanism can be used for the crystalline quality control of the 2D materials, using the spin embedded in the hBN as a probe.

Generalized Heisenberg-Type Magnetic Phenomena in Coordination Polymers with Nickel–Lanthanide Dinuclear Units

A new family of 3d–4f coordination polymers with the molecular formula [NiIILnIII(L)(dca)2(NO3)]n [Ln = Eu (1), Gd (2), Tb (3), Dy (4), and Ho (5); H2L = N,N′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)homopiperazine; dca = dicyanamide] has been synthesized in search for new single-molecule magnet (SMM) materials containing highly anisotropic lanthanides. The magnetic properties of these materials have been established by DC and AC magnetometry and explained quantitatively by comprehensive phenomenological modeling based on a generalized Heisenberg-type model, hypothesized previously based on first-principles calculations. Single-crystal X-ray diffraction has shown that the compounds are isostructural, with lanthanide atoms occupying a nine-coordination site with muffin-like geometry and individual NiII–LnIII units linked by dca anions. Other than the paramagnetic compound 1, 2–5 exhibit intra-unit ferromagnetic 3d–4f interactions, favorable for a large spin ground state. A slow field-induced relaxation of magnetization has been observed in compound 4 (only), displaying a substantial energy barrier of Ueff/kB = 26.2(5) K, below 6 K. This is attributed to an easy-plane anisotropy and is consistent with the relaxation in systems with a Kramers ground state doublet and hyperfine interactions.

Spectroscopic investigation of light strange S = −1 Λ and Σ and S = −2 Ξ baryons

The present study is dedicated to light-strange with strangeness S = −1 and isospin I = 0, with S = −1 and I = 1, and baryon with S = −2 and . In this study, the hypercentral constituent quark model with linear confining potential has been employed along with a first order correction term to obtain the resonance masses up to approximately 4 GeV. The calculated states include 1S-5S, 1P-4P, 1D-3D, 1F-2F, and 1G (in a few cases) along with all possible spin-parity assignments. Regge trajectories have been explored for the linearity of the calculated masses for and . Magnetic moments have been intensively studied for ground state spin and , in addition to the configuration mixing of the first negative parity state for . Lastly, the transition magnetic moments and radiative decay widths have been presented.

A Computational Study of the S2 State in the Oxygen-Evolving Complex of Photosystem II by Electron Paramagnetic Resonance Spectroscopy.

The S2 state produces two basic electron paramagnetic resonance signal types due to the manganese cluster in oxygen-evolving complex, which are influenced by the solvents, and cryoprotectant added to the photosystem II samples. It is presumed that a single manganese center oxidation occurs on S1 → S2 state transition. The S2 state has readily visible multiline and electron paramagnetic resonance signals and hence it has been the most studied of all the Kok cycle intermediates due to the ease of experimental preparation and stability. The S2 state was studied using electron paramagnetic resonance spectroscopy at X-band frequencies. The aim of this study was to determine the spin states of the signal. The multiline signal was observed to arise from a ground state spin ½ centre while the 4.1 signal generated at ≈140 K NIR illumination was proposed to arise from a spin center with rhombic distortion. The ‘ground’ state 4.1 signal was generated solely or by conversion from the multiline. The data analysis methods used involved numerical simulations of the experimental spectra on relevant models of the oxygen-evolving complex cluster. A strong focus in this paper was on the ‘ground’ state 4.1 signal, whether it is a rhombic spin state signal or an axial spin state signal. The data supported an X-band CW-EPR-generated 4.1 signal as originating from a near rhombic spin 5/2 of the S2 state of the PSII manganese cluster.

Unexpected Light-Induced Thermal Hysteresis in Matrix Embedded Low Cooperative Spin Crossover Microparticles

The embedding of spin-crossover micro- or nanocrystals in various surroundings dramatically changes their functionalities based on first-order spin transitions. The dampening of their internal cooperativity, together with introducing a new kind of interactions occurring at interfaces between spin-crossover particles and their environment, results in spectacular effects, as an enhanced hysteresis with non-cooperative transitions. In this work, we deal with the influence of the embedding matrix on the light-induced thermal hysteresis (LITH) in the case of spin-crossover microparticles of Fe(phen)2(NCS)2. Despite the low cooperativity of this compound, the competition between the continuous photoexcitation towards the metastable high spin state and the relaxation down to low spin ground state leads to a light-induced thermal hysteresis, with a quasi-static width of around 10 K. This unexpected hysteresis is explained by considering a switch-on/cutoff mechanism of the particle–matrix interactions in the framework of a mean-field approach based on negative external pressures, with Gaussian distributed variations and of an Ising-like model with various interactions with the environment. Additional first-order reversal curves measurements and corresponding calculated distributions are in line with relaxations under light and confirm the existence of a non-kinetic LITH.

1,3-Diradicals Embedded in Curved Paraphenylene Units: Singlet versus Triplet State and In-Plane Aromaticity.

Curved π-conjugated molecules and open-shell structures have attracted much attention from the perspective of fundamental chemistry, as well as materials science. In this study, the chemistry of 1,3-diradicals (DRs) embedded in curved cycloparaphenylene (CPPs) structures, DR-(n+3)CPPs (n = 0-5), was investigated to understand the effects of the curvature and system size on the spin-spin interactions and singlet versus triplet state, as well as their unique characteristics such as in-plane aromaticity. A triplet ground state was predicted for the larger 1,3-diradicals, such as the seven- and eight-paraphenylene-unit-containing diradicals DR-7CPP (n = 4) and DR-8CPP (n = 5), by quantum chemical calculations. The smaller-sized diradicals DR-(n+3)CPPs (n = 0-3) were found to possess singlet ground states. Thus, the ground-state spin multiplicity is controlled by the size of the paraphenylene cycle. The size effect on the ground-state spin multiplicity was confirmed by the experimental generation of DR-6CPP in the photochemical denitrogenation of its azo-containing precursor (AZ-6CPP). Intriguingly, a unique type of in-plane aromaticity emerged in the smaller-sized singlet states such as S-DR-4CPP (n = 1), as proven by nucleus-independent chemical shift calculations (NICS) and an analysis of the anisotropy of the induced current density (ACID), which demonstrate that homoconjugation between the 1,3-diradical moiety arises because of the curved and distorted bonding system.

Gapless Spin Wave Transport through a Quantum Canted Antiferromagnet

In the Landau levels of a two-dimensional electron system or when flat bands are present, e.g. in twisted van der Waals bilayers, strong electron-electron interaction gives rise to quantum Hall ferromagnetism with spontaneously broken symmetries in the spin and isospin sectors. Quantum Hall ferromagnets support a rich variety of low-energy collective excitations that are instrumental to understand the nature of the magnetic ground states and are also potentially useful as carriers of quantum information. Probing such collective excitations, especially their dispersion {\omega}(k), has been experimentally challenging due to small sample size and measurement constraints. In this work, we demonstrate an all-electrical approach that integrates a Fabry-P\'erot cavity with non-equilibrium transport to achieve the excitation, wave vector selection and detection of spin waves in graphene heterostructures. Our experiments reveal gapless, linearly dispersed spin wave excitations in the E = 0 Landau level of bilayer graphene, thus providing direct experimental evidence for a predicted canted antiferromagnetic order. We show that the gapless spin wave mode propagates with a high group velocity of several tens of km/s and maintains phase coherence over a distance of many micrometers. Its dependence on the magnetic field and temperature agree well with the hydrodynamic theory of spin waves. These results lay the foundation for the quest of spin superfluidity in this high-quality material. The resonant cavity technique we developed offers a powerful and timely method to explore the collective excitation of many spin and isospin-ordered many-body ground states in van der Waals heterostructures and open the possibility of engineering magnonic devices.

Optical spin-state polarization in a binuclear europium complex towards molecule-based coherent light-spin interfaces

The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ion (REI)-based molecular systems, whose quantum properties could be tuned taking advantage of molecular engineering strategies, are one of the systems actively pursued for the implementation of QIP schemes. Herein, we demonstrate the efficient polarization of ground-state nuclear spins—a fundamental requirement for all-optical spin initialization and addressing—in a binuclear Eu(III) complex, featuring inhomogeneously broadened 5D0 → 7F0 optical transition. At 1.4 K, long-lived spectral holes have been burnt in the transition: homogeneous linewidth (Γh) = 22 ± 1 MHz, which translates as optical coherence lifetime (T2opt) = 14.5 ± 0.7 ns, and ground-state spin population lifetime (T1spin) = 1.6 ± 0.4 s have been obtained. The results presented in this study could be a progressive step towards the realization of molecule-based coherent light-spin QIP interfaces.

Copper Complexes of the Tetradentate N,N′‐Bis(2‐amino‐3,5‐di‐tert‐butylphenyl)‐2,2′‐diaminobiphenyl Ligand

AbstractThe ligand N,N′‐bis(2‐amino‐3,5‐di‐tert‐butylphenyl)‐2,2′‐diaminobiphenyl was synthesized and coordinated to copper. Complex 1+ was structurally characterized, showing two deprotonated diiminobenzoquinone ligands coordinated to a single Cu(I) center. The paramagnetic complexes 1 and 12+ were generated and characterized by EPR and Vis‐NIR spectroscopy. Complex 1 exhibits an isotropic resonance at g=2.00, which is reminiscent of Cu(I) diiminosemiquinone species. The dication 12+ exhibits a metal‐based ground spin state and hence is described as a Cu(II) diiminobenzoquinone complex. Both 1 and 1+ show a NIR band (954, 980 nm) of high intensity (>20 mM−1 cm−1) assigned to ligand‐based charge transfer transitions.

STABILITY OF SKYRMIONS IN THE FRUSTRATED ANTIFERROMAGNETIC/FERROELECTRIC BILAYERS WITH THE TRIANGULAR LATTICE

The formation and conditions of stability of a skyrmions at the interface between a ferroelectric layer and antiferromagnetic layer with triangilar lattice and its phase transition are studied. All interactions between spins and polarizations are limited to nearest neighbors (NN). The antiferromagnetic exchange interaction among the spins inside antiferromagnetic layer will compete with the perpendicular interface interaction between adjacent layers. The ground state spin configuration at zero temperature is calculated by using the numerical high performance steepest descent method. The resulting configuration is non-collinear. Small values of external field yields small values of angles between spins in the plane so that the ground state configurations have antiferromagnetic and non collinear domains. We observe the creation of single spin vortices. We noted that for zero applied magnetic field the skyrmions in the antiferromagnetic/ferroelectric bilayers with triangular lattice can be created in the region of interface magnetoelectric interaction value between 0.85 and 1.95. The strong external magnetic field applied perpendicular to the interface with non-collinear Dzyaloshinskiy-Morya-like magnetoelectric interaction at the interface leads to remove the skyrmion phase and magnetic phase transitions. With increasing the interface magnetoelectric coupling, the skyrmion lattice disappear. We found the formation perfect skyrmion structure at non-zero external magnetic field and moderate values of magnetoelectric interaction. The skyrmions structure is stable in a large region of the interface magnetoelectric interaction between antiferromagnetic and ferroelectric films. The results of Monte Carlo simulations that we carried out confirm that observed skyrmions are stable up to a finite temperature.

A giant spin molecule with ninety-six parallel unpaired electrons

SummaryUnpaired electrons which are essential for organic radicals and magnetic materials are hardly to align parallel, especially upon the increasing of spin numbers. Here, we show that the antiferromagnetic interaction in the largest Cr(III)-RE (rare earth) cluster {Cr10RE18} leads to 96 parallel electrons, forming a ground spin state ST of 48 for RE = Gd. This is so far the third largest ground spin state achieved in one molecule. Moreover, by using the classical Monte Carlo simulation, the exchange coupling constants can be determined. Spin dynamics simulation reveals that the strong Zeeman effects of 18 Gd(III) ions stabilize the ground ferrimagnetic state and hinder the magnetization reversals of these spins. In addition, the dysprosium(III) analog is an exchange-biasing single-molecule magnet. We believe that the ferrimagnetic approach and analytical protocol established in this work can be applied generally in constructing and analyzing giant spin molecules.