Vibrational Modes of C_<60> Fullerene Adsorbed on Si(100)2×1 Surface Studied by High-Resolution Electron-Energy-Loss Spectroscopy

We have measured the inelastic electron-energy-loss spectra of C_ on the Si(100)2x1 surface in the infra-red energy range. If C_ is evaporated 5Å (approximately half a monolayer) on Si(100), a strong energy loss peak appears at 65 meV, and weak peaks and shoulders at 72, 144, and 175 meV. In the 12Å thick film, additional weak peaks at 96, 160, and 189 meV become more apparent. Intensities of these peaks are comparable to those of thick films measured by infra-red absorption and by Raman scattering spectroscopies. Moreover, we have measured the angle dependence of the inelastic electron intensity. These results suggest appreciable interactions between C_ and the dangling bonds of Si surface

Interfacial Dzyaloshinskii-Moriya interaction in epitaxial W/Co/Pt multilayers

Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered ferromagnetic films gives rise to non-colinear spin structures stabilizing magnetization configurations with nontrivial topology. In this work magnetization reversal, domain structure, and strength of DMI are related with the structure of W/Co/Pt multilayers grown by molecular beam epitaxy. Applied growth method enables fabrication of layered systems with higher crystalline quality than commonly applied sputtering techniques. As a result, a high value of D coefficient was determined from the aligned magnetic domain stripe structure, substantially exceeding 2 mJ/m2. The highest value of DMI value D$_{eff}$ = 2.64mj/m2 and strength of surface DMI parameter DS = 1.83pJ/m for N=10 has been observed. Experimental results coincide precisely with those obtained from structure based micromagnetic modelling and density functional theory calculations performed for well-defined layered stacks. This high value of DMI strength originates from dominating contributions of the interfacial atomic Co layers and additive character from both interface types

The molecular basis of tRNA selectivity by human pseudouridine synthase 3

Pseudouridine (Ψ), the isomer of uridine, is ubiquitously found in RNA, including tRNA, rRNA, and mRNA. Human pseudouridine synthase 3 (PUS3) catalyzes pseudouridylation of position 38/39 in tRNAs. However, the molecular mechanisms by which it recognizes its RNA targets and achieves site specificity remain elusive. Here, we determine single-particle cryo-EM structures of PUS3 in its apo form and bound to three tRNAs, showing how the symmetric PUS3 homodimer recognizes tRNAs and positions the target uridine next to its active site. Structure-guided and patient-derived mutations validate our structural findings in complementary biochemical assays. Furthermore, we deleted PUS1 and PUS3 in HEK293 cells and mapped transcriptome-wide Ψ sites by Pseudo-seq. Although PUS1-dependent sites were detectable in tRNA and mRNA, we found no evidence that human PUS3 modifies mRNAs. Our work provides the molecular basis for PUS3-mediated tRNA modification in humans and explains how its tRNA modification activity is linked to intellectual disabilities

Magnetic anisotropy changes in ultrathin Co films grown on vicinal sapphire substrates

The aim of the work is to study the magnetic anisotropy changes in epitaxial ultrathin Co films grown on vicinal sapphire substrates with different miscut angles. Changes of the in-plane magnetic anisotropy symmetry were deduced from magnetooptical hysteresis loops shape and angular dependence analysis of the resonance field measured in the sample plane. Two-fold and four-fold symmetry of the in-plane anisotropy was observed for different miscut angles. The experimental data are discussed taking into account the following energy contributions: (i) demagnetization; (ii) perpendicular uniaxial anisotropy (iii) and step-induced uniaxial anisotropy. Magnetic anisotropy constants are fitted to the experimental results for different miscut angles

Platinum overlayer-induced changes of magnetic and magneto-optical properties of ultrathin Co layer

Magneto-optical and magnetic properties of Au/Co-wedge/Pt-wedge/Au were investigated as functions of component layer thicknesses. The remanence, coercivity field and saturation of both rotation and ellipticity were deduced from the shape analysis of the magnetic hysteresis loops measured at different positions of the sample by means of the magneto-optical polar Kerr effect magnetometer. For low thickness of platinum overlayer Co-thickness range with perpendicular anisotropy increases, and very high peak of coercivity field was observed. These phenomena are explained in terms of the ternary Co–Pt–Au alloy occurrence with large anisotropy at interface

Transverse magneto-optical Kerr effect measured using phase modulation

An ellipsometric configuration for measurement of the complex transverse magneto-optical Kerr effect is described that uses a photoelastic modulator (PEM). The real and imaginary parts of the complex transverse Kerr effect are represented as small perturbations of ellipsometric angles psi and Delta. The measurement, based on null ellipsometry and zone averaging, gives high signal typical for modulation techniques and insensitivity to other magnetisation components and system imperfections. The method is demonstrated by the measurement of transverse component during magnetisation reversal in a thin cobalt film.Web of Science1art. no. 0601

Domain structures and magnetization processes in thin Co films with in-plane anisotropy

The magnetization reversal and domain structures in thin Co films in the thickness range 2 nm<d<100 nm whith in-plane magnetic anisotropy were studied. Both magneto-optical (MO) vector magnetometry and MO microscopy were used. The crossover of in-plane anisotropy symmetry from two-fold to six-fold were observed with increase of Co layer thickness from 2 nm to 100 nm. The evolution of the domain structure during the magnetization reversal process was studied for different orientations of magnetic field relatively to anisotropy easy axis using longitudinal Kerr MO microscope

Influence of V and Mo overlayer on magneto-optical Kerr effect in ultrathin Co films

A method for characterization of sub-nanometer thick Co/V and Co/Mo interfaces is proposed that uses magneto-optical ellipsometry. Both the polar Kerr rotation and ellipticity are fitted simultaneously to different models of interface layer. The magneto-optical data are measured for varying thicknesses of the cobalt layer and overlayer by scanning of a laser beam over the samples with two orthogonal wedges. Decrease of magneto-optical effect at both interfaces Co/V and Co/Mo were observed, which corresponds to interface layers of thicknesses ranging from one to two monoatomic layers. In the case of vanadium, the interface layer is sharper and can be explained either by reduced magnetic moment of cobalt, or by anti-parallel magnetic moment of vanadium near the Co/V interface