Internal Dynamics of Ionic Liquids over a Broad Temperature Range—The Role of the Cation Structure

1H and 19F spin-lattice relaxation experiments have been performed for a series of ionic liquids sharing the same anion: bis(trifluoromethanesulfonyl)imide but including cations of different alkyl chain lengths: butyltriethylammonium, triethyloctylammonium, dodecyltriethylammo-nium and hexadecyltriethylammonium. The studies have been carried out in the temperature range from 383 to 108 K at the resonance frequency of 200 MHz (for 1H). A quantitative analysis of the relaxation data has revealed two dynamical processes for both kinds of ions. The dynamics have been successfully modeled in terms of the Arrhenius law. The timescales of the dynamical processes and their temperature evolution have been discussed in detail, depending on the structure of the cation.

Molecular interaction and partitioning in α-keratin using 1 H NMR spin-lattice ( T 1 ) relaxation times

The interactions between small molecules and keratins are poorly understood. In this paper, a nuclear magnetic resonance method is presented to measure changes in the 1 H T 1 relaxation times of small molecules in human hair keratin to quantify their interaction with the fibre. Two populations of small-molecule compounds were identified with distinct relaxation times, demonstrating the partitioning of the compounds into different keratin environments. The changes in relaxation time for solvent in hair compared with bulk solvent were shown to be related to the molecular weight (MW) and the partition coefficient, LogP, of the solvent investigated. Compounds with low MWs and high hydrophilicities had greater reductions in their T 1 relaxation times and therefore experienced increased interactions with the hair fibre. The relative population sizes were also calculated. This is a significant step towards modelling the behaviour of small molecules in keratinous materials and other large insoluble fibrous proteins.

Low energy electrodynamics of CrI3 layered ferromagnet

We report on the optical properties from terahertz (THz) to Near-Infrared (NIR) of the layered magnetic compound CrI3 at various temperatures, both in the paramagnetic and ferromagnetic phase. In the NIR spectral range, we observe an insulating electronic gap around 1.1 eV which strongly hardens with decreasing temperature. The blue shift observed represents a record in insulating materials and it is a fingerprint of a strong electron-phonon interaction. Moreover, a further gap hardening is observed below the Curie temperature, indicating the establishment of an effective interaction between electrons and magnetic degrees of freedom in the ferromagnetic phase. Similar interactions are confirmed by the disappearance of some phonon modes in the same phase, as expected from a spin-lattice interaction theory. Therefore, the optical properties of CrI3 reveal a complex interaction among electronic, phononic and magnetic degrees of freedom, opening many possibilities for its use in 2-Dimensional heterostructures.

Skyrmion-Antiskyrmion Racetrack Memory in Rank-One DMI Materials

Chiral magnetic skyrmions, localized and topologically protected vortex-like magnetic textures that can be found in chiral magnets, are currently under intense study as an entity for information storage and processing. A recent study showed that so-called rank-one materials can host both skyrmions and antiskyrmions at the same energy. In such systems the Dzyaloshinskii-Moriya interaction, in general a tensorial quantity, is reduced to only one non-zero component. The presence of both skyrmions and antiskyrmions allows for the investigation of the possible interplay between them. Here, we investigate the stability and interaction of skyrmions and antiskyrmions as well as their transport properties subject to spin-orbit torque for a model system described by an atomistic spin-lattice Hamiltonian employing the simulation software Spirit. The spin-orbit torque driven spin-dynamics described by the Landau-Lifshitz-Gilbert equation is compared to the effective one of the Thiele equation. We demonstrate that, even though skyrmions and antiskyrmions can be seen as antiparticles, a rather dense arrangement of both along a memory track is possible, enabling their use as representations of the binary data bits “0” and “1” in a memory device.

Twofold symmetry of c-axis resistivity in topological kagome superconductor CsV3Sb5 with in-plane rotating magnetic field

In transition metal compounds, due to the interplay of charge, spin, lattice and orbital degrees of freedom, many intertwined orders exist with close energies. One of the commonly observed states is the so-called nematic electron state, which breaks the in-plane rotational symmetry. This nematic state appears in cuprates, iron-based superconductor, etc. Nematicity may coexist, affect, cooperate or compete with other orders. Here we show the anisotropic in-plane electronic state and superconductivity in a recently discovered kagome metal CsV3Sb5 by measuring c-axis resistivity with the in-plane rotation of magnetic field. We observe a twofold symmetry of superconductivity in the superconducting state and a unique in-plane nematic electronic state in normal state when rotating the in-plane magnetic field. Interestingly these two orders are orthogonal to each other in terms of the field direction of the minimum resistivity. Our results shed new light in understanding non-trivial physical properties of CsV3Sb5.

Mixing, Domains, and Fast Li-ion Dynamics in Ternary Li-Sb-Bi Battery Anode Alloys

Antimony and bismuth can both alloy with up to three molar equivalents of lithium and are therefore attractive candidates for replacing graphite in Li-ion battery anodes. Li3Sb and Li3Bi have the same cubic structure (Fm3 ̅m), but the ternary Li-Sb-Bi system has not been studied. We synthesized Li3(SbxBi1-x) with different Sb mole fractions at room temperature by ball-milling. These ternary alloys all have cubic crystal structures, as determined by XRD, but show a tendency towards phase segregation for x = 0.25 and 0.50. For x = 0.25, the lattice parameter presents a clear positive deviation from Vegard’s law in XRD, while for x = 0.50, XRD reveals two phases after milling, with the Bi-rich minority phase diminishing after thermal annealing. Solid-state nuclear magnetic resonance spectroscopy provides evidence for a Sb-enriched environment around the Li atoms for Li3Sb0.25Bi0.75, and nuclear spin-lattice relaxation measurements of the binary and ternary alloy phases point to low activation energies and rapid Li ion diffusion in Li3Bi.

Phenomenological explanation of spontaneous polarisation and onset ferroelectric Phase transition in RbH2AsO4 (RDA) crystal

By applying two-time thermal dependent Zuberav’s statistical, retarded Green function approach and modified earlier simple PLCM model Hamiltonian by adding some extra terms into it, like third-order and fourth-order, phonon anharmonic interactions, direct spin-spin terms, extra spin-lattice terms, and four body interaction terms, for theoretical investigation of thermal dependent spontaneous polarization and ferroelectric phase transition in the first-order phase, of RbH2AsO4crystal. It undergoes a ferroelectric phase transition at 109.9K. With the help of Dyson’s equation in the Mean-Field Approximation (MFA), theoretical formulae are obtained for electrical permittivity, tangent delta, Cochran’s mode frequency, spontaneous polarization, and response function. Model values are fitted for the above physical parameters to obtain variations with temperature. A comparison of theoretical finding has been made with the experimental finding reported by Blinc et al [12], and Zolototrubov et al[8].