Quantum Spin Dynamics Due to Strong Kitaev Interactions in the Triangular-Lattice Antiferromagnet CsCeSe_{2}.

The extraordinary properties of the Kitaev model have motivated an intense search for new physics in materials that combine geometrical and bond frustration. In this Letter, we employ inelastic neutron scattering, spin wave theory, and exact diagonalization to study the spin dynamics in the perfect triangular-lattice antiferromagnet (TLAF) CsCeSe_{2}. This material orders into a stripe phase, which is demonstrated to arise as a consequence of the off-diagonal bond-dependent terms in the spin Hamiltonian.

Thirty Years of Hide-and-Seek: Capturing Abundant but Elusive M@(8)-C Isomer, and the Study of Magnetic Anisotropy Induced in Dy Ion by the Fullerene π-Ligand.

Our knowledge about endohedral metallofullerenes (EMFs) is restricted to the structures with sufficient kinetic stability to be extracted from the arc-discharge soot and processed by chromatographic and structural techniques. For the most abundant rare-earth monometallofullerene M@C, experimental studies repeatedly demonstrated (9) and (6) carbon cage isomers, while computations predicted equal stability of the "missing" (8) isomer. Here we report that this isomer is indeed formed but has not been recovered from soot using standard protocols.

Kinetically controlled metal-elastomer nanophases for environmentally resilient stretchable electronics.

Nanophase mixtures, leveraging the complementary strengths of each component, are vital for composites to overcome limitations posed by single elemental materials. Among these, metal-elastomer nanophases are particularly important, holding various practical applications for stretchable electronics. However, the methodology and understanding of nanophase mixing metals and elastomers are limited due to difficulties in blending caused by thermodynamic incompatibility.

Covalency magnetic axiality in Nd molecular magnets: Nd-photoluminescence, strong ligand-field, and unprecedented nephelauxetic effect in fullerenes NdMN@C (M = Sc, Lu, Y).

Nd-based nitride clusterfullerenes NdMN@C with rare-earth metals of different sizes (M = Sc, Y, Lu) were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X-ray diffraction revealed a very short Nd-N bond length in NdScN@C. For Lu and Y analogs, the further shortening of the Nd-N bond and pyramidalization of the NdMN cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage.

Improving the molecular spin qubit performance in zirconium MOF composites by mechanochemical dilution and fullerene encapsulation.

Enlarging the quantum coherence times and gaining control over quantum effects in real systems are fundamental for developing quantum technologies. Molecular electron spin qubits are particularly promising candidates for realizing quantum information processing due to their modularity and tunability. Still, there is a constant search for tools to increase their quantum coherence times.

Flexomagnetism and vertically graded Néel temperature of antiferromagnetic CrO thin films.

Antiferromagnetic insulators are a prospective materials platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A magnetomechanical coupling in antiferromagnets offers vast advantages in the control and manipulation of the primary order parameter yet remains largely unexplored. Here, we discover a new member in the family of flexoeffects in thin films of CrO.

Vibrational anatomy of C, C, and C fullertubes: probing Frankenstein's skeletal structures of fullerene head endcaps and nanotube belt midsection.

Fullertubes are tubular fullerenes with nanotube-like middle section and fullerene-like endcaps. To understand how this intermediate form between spherical fullerenes and nanotubes is reflected in the vibrational modes, we performed comprehensive studies of IR and Raman spectra of fullertubes C-, C-, and C-. An excellent agreement between experimental and DFT-computed spectra enabled a detailed vibrational assignment and allowed an analysis of the localization degree of the vibrational modes in different parts of fullertubes.

Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb@CN.

Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb@CN, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb@CN exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.

Conformational preferences of endohedral metallofullerenes on Ag, Au, and MgO surfaces: Theoretical studies.

In this report, we study the ordering of C , Sc N@C , and Dy ScN@C molecules on different metallic and dielectric surfaces such as Ag(100), Au(111), and MgO(100). By using DFT techniques, we can classify different types of cage-to-surface arrangements and their relative energies. Using a proposed homogenous sampling of the conformational space for the M N cluster, we determine a potential energy map that is capable of providing a structural distribution for a given energy window.

Metallofullerene single-molecule magnet DyO@(5)-C with a strong antiferromagnetic Dy⋯Dy coupling.

Dysprosium-oxide clusterfullerene DyO@(5)-C is a single-molecule magnet featuring antiferromagnetic superexchange Dy⋯Dy coupling the μ-O bridge, the strongest of its kind among {Dy} complexes with non-radical bridges.

Imaging the Single-Electron Ln-Ln Bonding Orbital in a Dimetallofullerene Molecular Magnet.

Chemically robust single-molecule magnets (SMMs) with sufficiently high blocking temperatures T are among the key building blocks for the realization of molecular spintronic or quantum computing devices. Such device applications require access to the magnetic system of a SMM molecule by means of electronic transport, which primarily depends on the interaction of magnetic orbitals with the electronic states of the metallic electrodes. Scanning tunneling microscopy in combination with ab initio calculations allows to directly address the unoccupied component of the single-electron molecular orbital that mediates the ferromagnetic exchange coupling between two 4f ions within a lanthanide endohedral dimetallofullerene deposited on a graphene surface.

Stripe-magnetic order in the triangular-lattice antiferromagnet KCeS.

Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO, NaYbS, and NaYbSe, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeSexhibits magnetic order below= 400 mK, which was so far identified only in thermodynamic measurements.

Metallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer.

We report on the discovery and detailed exploration of the unconventional photo-switching mechanism in metallofullerenes, in which the energy of the photon absorbed by the carbon cage π-system is transformed to mechanical motion of the endohedral cluster accompanied by accumulation of spin density on the metal atoms. Comprehensive photophysical and electron paramagnetic resonance (EPR) studies augmented by theoretical modelling are performed to address the phenomenon of the light-induced photo-switching and triplet state spin dynamics in a series of Y Sc N@C ( = 0-3) nitride clusterfullerenes. Variable temperature and time-resolved photoluminescence studies revealed a strong dependence of their photophysical properties on the number of Sc atoms in the cluster.

Terahertz Magneto-Optical Excitations of the sd-Hybrid States of Lithium Nitridocobaltate Li(LiCo)N.

We report the results of the experimental and theoretical study of the magnetic anisotropy of single crystals of the Co-doped lithium nitride Li(LiCo)N with = 0.005, 0.01, and 0.

Magnetic Hysteresis at 10 K in Single Molecule Magnet Self-Assembled on Gold.

Tremendous progress in the development of single molecule magnets (SMMs) raises the question of their device integration. On this route, understanding the properties of low-dimensional assemblies of SMMs, in particular in contact with electrodes, is a necessary but difficult step. Here, it is shown that fullerene SMM self-assembled on metal substrate from solution retains magnetic hysteresis up to 10 K.

Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene DyS@C.

Two isomers of metallofullerene DyS@C with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature. Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples, the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy⋯Dy inter-actions. A comparison of different methods to determine the energy difference between ferromagnetic and antiferromagnetic states showed that sub-Kelvin hysteresis gives the most robust and reliable values.

Shape-adaptive single-molecule magnetism and hysteresis up to 14 K in oxide clusterfullerenes DyO@C and DyO@C with fused pentagon pairs and flexible Dy-(μ-O)-Dy angle.

Dysprosium oxide clusterfullerenes DyO@C(10528)-C and DyO@C(13333)-C are synthesized and characterized by single-crystal X-ray diffraction. Carbon cages of both molecules feature two adjacent pentagon pairs. These pentalene units determine positions of endohedral Dy ions hence the shape of the DyO cluster, which is bent in DyO@C but linear in DyO@C.

Caught in Phase Transition: Snapshot of the Metallofullerene ScN@C Rotation in the Crystal.

The molecular structure of ScN@(7854)-C was determined by single-crystal X-ray diffraction. Variable-temperature X-ray diffraction analysis unraveled the details of the phase transition caused by the temperature-driven jumplike rotation of the fullerene cage between two orientations. Whereas in the lower-temperature 2/ phase the fullerene predominantly occupies one orientation, two orientations become equally occupied in the higher-temperature 2/ phase.

Substrate-Independent Magnetic Bistability in Monolayers of the Single-Molecule Magnet Dy ScN@C on Metals and Insulators.

Magnetic hysteresis is demonstrated for monolayers of the single-molecule magnet (SMM) Dy ScN@C deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy ScN@C adsorbed on Au(111) were studied by STM. X-ray magnetic CD studies show that the Dy ScN@C monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy ScN cluster depends strongly on the surface.

Single-Molecule Magnets DyM N@C and Dy MN@C (M=Sc, Lu): The Impact of Diamagnetic Metals on Dy Magnetic Anisotropy, Dy⋅⋅⋅Dy Coupling, and Mixing of Molecular and Lattice Vibrations.

The substitution of scandium in fullerene single-molecule magnets (SMMs) DySc N@C and Dy ScN@C by lutetium has been studied to explore the influence of the diamagnetic metal on the SMM performance of dysprosium nitride clusterfullerenes. The use of lutetium led to an improved SMM performance of DyLu N@C , which shows a higher blocking temperature of magnetization (T =9.5 K), longer relaxation times, and broader hysteresis than DySc N@C (T =6.

Magnetism in Ln molecular systems with 4f/valence-shell interplay (FV-magnetism).

The hunt for high-performance single-molecule magnets (SMM) revealed that atomic and molecular lanthanide systems combining 4f-shell and valence magnetism (FV-magnetism) may show magnetic bistability up to unexpectedly high temperatures. Here we rationalize the stability of the magnetism in the FV-systems from first principles on the example of LnII(CpiPr5)2 molecules.

Single Molecule Magnetism with Strong Magnetic Anisotropy and Enhanced Dy∙∙∙Dy Coupling in Three Isomers of Dy-Oxide Clusterfullerene DyO@C.

A new class of single-molecule magnets (SMMs) based on Dy-oxide clusterfullerenes is synthesized. Three isomers of DyO@C with (6), (8), and (9) cage symmetries are characterized by single-crystal X-ray diffraction, which shows that the endohedral Dy-(µ-O)-Dy cluster has bent shape with very short Dy-O bonds. DyO@C isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage.

Effect of the Diamagnetic Single-Crystalline Host on the Angular-Resolved Electron Nuclear Double Resonance Experiments: Case of Paramagnetic [BuN][Cu(opba)] Embedded in Diamagnetic [BuN][Ni(opba)].

The electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) spectroscopies are frequently used to determine hyperfine () and quadrupole () tensors for the paramagnetic transition-metal complexes, which knowledge enables estimation of the spin density distribution in the complex and the assessment of magnetic exchange pathways in polynuclear molecular networks. The most accurate results can be obtained if paramagnetic complexes are isolated in a single-crystalline diamagnetic host. In this work we were able to detect angle-resolved ESR/ENDOR spectra of the paramagnetic [BuN][Cu(opba)] (opba = -phenylenebis(oxamato) complex hosted by the single crystal of diamagnetic [BuN][Ni(opba)], which allow recovery of , , and -tensors, all at once.

Single-Electron Lanthanide-Lanthanide Bonds Inside Fullerenes toward Robust Redox-Active Molecular Magnets.

A characteristic phenomenon of lanthanide-fullerene interactions is the transfer of metal valence electrons to the carbon cage. With early lanthanides such as La, a complete transfer of six valence electrons takes place for the metal dimers encapsulated in the fullerene cage. However, the low energy of the σ-type Ln-Ln bonding orbital in the second half of the lanthanide row limits the Ln → fullerene transfer to only five electrons.