The exploration of 1D magnetism, frequently portrayed as spin chains, constitutes an actively pursued research field that illuminates fundamental principles in many-body problems and applications in magnonics and spintronics. The inherent reduction in dimensionality often leads to robust spin fluctuations, impacting magnetic ordering and resulting in novel magnetic phenomena. Here, structural, magnetic, and optical properties of highly anisotropic 2D van der Waals antiferromagnets that uniquely host spin chains are explored. First-principle calculations reveal that the weakest interaction is interchain, leading to essentially 1D magnetic behavior in each layer. With the additional degree of freedom arising from its anisotropic structure, the structure is engineered by alloying, varying the 1D spin chain lengths using electron beam irradiation, or twisting for localized patterning, and spin textures are calculated, predicting robust stability of the antiferromagnetic ordering. Comparing with other spin chain magnets, these materials are anticipated to bring fresh perspectives on harvesting low-dimensional magnetism.

• Klíčová slova
• 1D magnetism, 2D magnets, 2D materials, scanning transmission electron microscopy,
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH

Magnetism in two dimensions is traditionally considered an exotic phase mediated by spin fluctuations, but far from collinearly ordered in the ground state. Recently, 2D magnetic states have been discovered in layered van der Waals compounds. Their robust and tunable magnetic state by material composition, combined with reduced dimensionality, foresee a strong potential as a key element in magnetic devices. Here, a class of 2D magnets based on metallic chlorides is presented. The magnetic order survives on top of a metallic substrate, even down to the monolayer limit, and can be switched from perpendicular to in-plane by substituting the metal ion from iron to nickel. Using functionalized STM tips as magnetic sensors, local exchange fields are identified, even in the absence of an external magnetic field. Since the compounds are processable by molecular beam epitaxy techniques, they provide a platform with large potential for incorporation into current device technologies.

• Klíčová slova
• 2D material, XMCD, ferromagnetism, nickelocene, transition metal halides, van der waals material,
• Publikační typ
• časopisecké články MeSH

A prominent characteristic of 2D magnetic systems is the enhanced spin fluctuations, which reduce the ordering temperature. We report that a magnetic field of only 1000th of the Heisenberg superexchange interaction can induce a crossover, which for practical purposes is the effective ordering transition, at temperatures about 6 times the Néel transition in a site-diluted two-dimensional anisotropic quantum antiferromagnet. Such a strong magnetic response is enabled because the system directly enters the antiferromagnetically ordered state from the isotropic disordered state, skipping the intermediate anisotropic stage. The underlying mechanism is achieved on a pseudospin-half square lattice realized in the [(SrIrO3)1/(SrTiO3)2] superlattice thin film that is designed to linearly couple the staggered magnetization to external magnetic fields by virtue of the rotational symmetry-preserving Dzyaloshinskii-Moriya interaction. Our model analysis shows that the skipping of the anisotropic regime despite finite anisotropy is due to the enhanced isotropic fluctuations under moderate dilution.

• Klíčová slova
• 2D antiferromagnet, extraordinary magnetic response, heterostructure thin film, magnetic dilution,
• Publikační typ
• časopisecké články MeSH

Emergent quantum phenomena in two-dimensional van der Waal (vdW) magnets are largely governed by the interplay between exchange and Coulomb interactions. The ability to precisely tune the Coulomb interaction enables the control of spin-correlated flat-band states, band gap, and unconventional magnetism in such strongly correlated materials. Here, we demonstrate a gate-tunable renormalization of spin-correlated flat-band states and bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene. Our gate-dependent scanning tunneling spectroscopy (STS) studies reveal that the interflat-band spacing and bandgap of CrBr3 can be continuously tuned by 120 and 240 meV, respectively, via electrostatic injection of carriers into the hybrid CrBr3/graphene system. This can be attributed to the self-screening of CrBr3 arising from the gate-induced carriers injected into CrBr3, which dominates over the weakened remote screening of the graphene substrate due to the decreased carrier density in graphene. Precise tuning of the spin-correlated flat-band states and bandgap in 2D magnets via electrostatic modulation of Coulomb interactions not only provides effective strategies for optimizing the spin transport channels but also may exert a crucial influence on the exchange energy and spin-wave gap, which could raise the critical temperature for magnetic order.

• Klíčová slova
• 2D magnetic insulator, STM, band renormalization, flat band, gate-tunable device,
• Publikační typ
• časopisecké články MeSH

Congenital epulis is a rare benign oral cavity tumor that usually arises from the maxillary alveolar mucosa. It is also known as congenital gingival granular cell tumor. Prenatal diagnosis is uncommon and mostly confined to the third trimester. We report a case of congenital epulis, which was referred to our department at 35 weeks of gestation. Both images from our prenatal 2D/3D ultrasound (including Doppler technique) and magnetic resonance examination are presented. A baby girl weighing 2,800 g was delivered spontaneously at 36 weeks and 1 day. The newborn had to be intubated immediately after delivery. A simple excision of the mass was performed on the first day of neonatal life after clinical examination by our pediatric stomatologists confirmed the presence of a tumor resembling epulis. The correctness of this diagnosis was subsequently confirmed by histogenesis. Photographs from the operating room show the postnatal appearance of the tumor. The baby was discharged at the age of 19 days and has remained well at follow-up controls.

• MeSH
• dospělí MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• nádor z granulárních buněk diagnóza   diagnostické zobrazování   embryologie   chirurgie   MeSH
• nádory dásní diagnóza   diagnostické zobrazování   embryologie   chirurgie   MeSH
• novorozenec MeSH
• prenatální diagnóza * MeSH
• těhotenství MeSH
• třetí trimestr těhotenství MeSH
• ultrasonografie dopplerovská barevná MeSH
• ultrasonografie prenatální MeSH
• výsledek terapie MeSH
• zobrazování trojrozměrné MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• novorozenec MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• práce podpořená grantem MeSH

The present widespread tomographic techniques based on computed tomography (CT), magnetic resonance imaging (MRI) and automatic 2D and 3D reconstructions also involve numerous new points of view for planning surgical techniques in orthopaedy. These require efficient pre- and post-processing methods. By pre-processing and post-processing is meant both the generation of a finite element mesh that numerically models human joints and the visualization of the results obtained as required by the surgeon. Since the numerical reconstructions of human joints are based on the finite element approximation of contact problems assuming linear elasticity, the main goal of pre-processing is to generate triangular (2D) and tetrahedral (3D) meshes of objects with a 'reasonable' boundary-human joints. In our paper we restrict ourselves, for the sake of simplicity, to polygonal (resp. polyhedral) objects. The idea of preprocessing is based on the modified method of Delaunay Mangulalia and on the so-called relaxation technique. After the generation of the finite element mesh and after numerical simulation of surgical problems of orthopaedy, the results obtained as stress-strain fields, temperature, etc. may be visualized in a graphical form on the computer screen as well as on other media.

• MeSH
• artrografie MeSH
• biologické modely * MeSH
• klouby patologie   chirurgie   MeSH
• kosti a kostní tkáň diagnostické zobrazování   patologie   chirurgie   MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• mechanický stres MeSH
• ortopedie MeSH
• počítačová grafika MeSH
• počítačová rentgenová tomografie MeSH
• počítačová simulace * MeSH
• počítačové zpracování obrazu MeSH
• pružnost MeSH
• tělesná teplota MeSH
• terapie s pomocí počítače MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp2-conjugated diradical motifs embedded in an sp3 matrix and superexchange interactions via -OH functionalization.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Phonons with chirality determine the optical helicity of inelastic light scattering processes due to their nonzero angular momentum. Here it is shown that 2D magnetic CrBr3 hosts chiral phonons at the Brillouin-zone center. These chiral phonons are linear combinations of the doubly-degenerate Eg phonons, and the phonon eigenmodes exhibit clockwise and counterclockwise rotational vibrations corresponding to angular momenta of l = ± 1. Such Eg chiral phonons completely switch the polarization of incident circularly polarized light. On the other hand, the non-degenerate non-chiral Ag phonons display a giant magneto-optical effect under an external out-of-plane magnetic field, rotating the plane of polarization of the scattered linearly polarized light. The corresponding degree of polarization of the scattered light changes from 91% to -68% as the magnetic field strength increases from 0 to 5 T. In contrast, the chiral Eg modes display no field dependence. The results lay a foundation for the study of phonon chirality and magneto-optical phenomena in 2D magnetic materials, as well as their related applications, such as the phonon Hall effect, topological photonics, and Raman lasing.

• Klíčová slova
• CrBr 3 ferromagnet, chiral phonons, magneto-optical effect, pseudoangular momentum, spin-phonon coupling,
• Publikační typ
• časopisecké články MeSH

The spin transport across a zero-dimensional (0D) single-molecule sandwiched by two-dimensional (2D) van der Waals (vdW) ferromagnetic electrodes may open vast opportunities to create novel mixed-dimensional spintronics devices. However, this remains unexplored yet. Inspired by the recent discovery of 2D intrinsic ferromagnets Fe3GeTe2, using first-principles spin transport calculations, we show that single-molecule junctions based on Fe3GeTe2 can yield perfect spin filtering and a significant magnetoresistance (MR) of up to ∼6075%. This remarkable MR is more than 2 orders of magnitude higher than the MR obtained for the corresponding junctions with conventional ferromagnetic metals (e.g., Ni, Fe, and Co). We demonstrate the results of two representative examples that are feasible in the experiments: (i) A benzene or (ii) bezenedithiol (BDT) connected either through a scanning tunneling microscope or break-junction setups. We find that the conductance of BDT junctions is more than 10 times larger than that of the benzene junction due to a much stronger hybridization effect at the molecule-metal interfaces. The key mechanism of the perfect spin filtering and large MR in single-molecule junctions is mainly determined by the intrinsic properties of Fe3GeTe2 electrodes, while the actual conductance is determined by the hybridization strength of the majority spin channel at the molecule-metal interfaces. It is also predicted that the perfect spin filtering and the remarkably huge MR are highly insensitive to structural variations, interface defects, and stacking orders of the electrodes. Our results provide important insights for expanding molecular spintronics platforms from conventional ferromagnetic metals to new 2D vdw magnets.

• Klíčová slova
• Fe3GeTe2, first-principles calculations, magnetoresistance, molecular junctions, spin filtering,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Cardiovascular magnetic resonance (CMR) 2D feature tracking (FT) left ventricular (LV) myocardial strain has seen widespread use to characterize myocardial deformation. Yet, validation of CMR FT measurements remains scarce, particularly for regional strain. Therefore, we aimed to perform intervendor comparison of 3 different FT software against tagging. METHODS: In 61 subjects (18 healthy subjects, 18 patients with chronic myocardial infarction, 15 with dilated cardiomyopathy, and 10 with LV hypertrophy due to hypertrophic cardiomyopathy or aortic stenosis) were prospectively compared global (G) and regional transmural peak-systolic Lagrangian longitudinal (LS), circumferential (CS) and radial strains (RS) by 3 FT software (cvi42, Segment, and Tomtec) among each other and with tagging at 3T. We also evaluated the ability of regional LS, CS, and RS by different FT software vs tagging to identify late gadolinium enhancement (LGE) in the 18 infarct patients. RESULTS: GLS and GCS by all 3 software had an excellent agreement among each other (ICC = 0.94-0.98 for GLS and ICC = 0.96-0.98 for GCS respectively) and against tagging (ICC = 0.92-0.94 for GLS and ICC = 0.88-0.91 for GCS respectively), while GRS showed inconsistent agreement between vendors (ICC 0.10-0.81). For regional LS, the agreement was good (ICC = 0.68) between 2 vendors but less vs the 3rd (ICC 0.50-0.59) and moderate to poor (ICC 0.44-0.47) between all three FT software and tagging. Also, for regional CS agreement between 2 software was higher (ICC = 0.80) than against the 3rd (ICC = 0.58-0.60), and both better agreed with tagging (ICC = 0.70-0.72) than the 3rd (ICC = 0.57). Regional RS had more variation in the agreement between methods ranging from good (ICC = 0.75) to poor (ICC = 0.05). Finally, the accuracy of scar detection by regional strains differed among the 3 FT software. While the accuracy of regional LS was similar, CS by one software was less accurate (AUC 0.68) than tagging (AUC 0.80, p < 0.006) and RS less accurate (AUC 0.578) than the other two (AUC 0.76 and 0.73, p < 0.02) to discriminate segments with LGE. CONCLUSIONS: We confirm good agreement of CMR FT and little intervendor difference for GLS and GCS evaluation, with variable agreement for GRS. For regional strain evaluation, intervendor difference was larger, especially for RS, and the diagnostic performance varied more substantially among different vendors for regional strain analysis.

• Klíčová slova
• Feature tracking, Magnetic resonance imaging, Strain, Tagging,
• MeSH
• funkce levé komory srdeční MeSH
• gadolinium MeSH
• kontrastní látky * MeSH
• lidé MeSH
• magnetická rezonance kinematografická * MeSH
• magnetická rezonanční spektroskopie MeSH
• prediktivní hodnota testů MeSH
• reprodukovatelnost výsledků MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• gadolinium MeSH
• kontrastní látky * MeSH