Search results for " electrons"
showing 10 items of 1168 documents
Photoabsorption and MXCD in photoemission microscopy for characterisation of advanced materials
1999
Abstract We applied chemical and magnetic sensitive photoemission electron microscopy (PEEM) to investigate surfaces of advanced materials. PEEM at low photon energies provides a high spatial resolution, but suffers from the lack of information about the chemical composition of the imaged surface. Such information can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired and subtracted microscopic images using photon energies just below and at the edges. The resulting difference gives a micro-image of the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of secondary electrons in…
Long-Range Order Induced by Intrinsic Repulsion on an Insulating Substrate
2015
An ordered arrangement of molecular stripes with equidistant appearance is formed upon the adsorption of 3-hydroxybenzoic acid onto calcite (10.4) held at room temperature. In a detailed analysis of the next-neighbor stripe distances measured in noncontact atomic force microscopy images at various molecular coverages, we compare the observed stripe arrangement with a random arrangement of noninteracting stripes. The experimentally obtained distance distribution deviates substantially from what is expected for a random distribution of noninteracting stripes, providing direct evidence for the existence of a repulsive interaction between the stripes. At low molecular coverage, where the averag…
Electron-phonon heat transport in degenerate Si at low temperatures
2004
The thermal conductance between electrons and phonons in a solid state system becomes comparatively weak at sub‐Kelvin temperatures. In this work five batches of thin heavily doped silicon‐on‐insulator samples with the electron concentration in the range of 2.0–16 × 1019 cm–3 were studied. Below 1 K all the samples were in the dirty limit of the thermal electron‐phonon coupling, where the thermal phonon wavelength exceeds the electron mean free path. The heat flow between electrons and phonons is proportional to (T6e–T6ph), where Te (Tph) is the electron (phonon) temperature. The constant of proportionality of the heat flow strongly depends on the electron concentration and its magnitude is…
Long-range magnetic order in the porous metal–organic framework Ni(pyrazine)[Pt(CN)4]
2017
A combined study involving DFT calculations, neutron scattering, heat capacity and magnetic measurements at very low temperatures demonstrates the long-range magnetic ordering of Ni(pyrazine)[Pt(CN)4] below 1.9 K, describing its antiferromagnetic spin arrangement. This compound belongs to the family of porous coordination polymers M(pyrazine)[Pt(CN)4] (M = divalent metal), renowned for showing interesting combinations of porosity and magnetic properties. The possibility of including long-range magnetic ordering, one of the most pursued functional properties, opens new perspectives for the multifunctionality of this class of compounds.
Room temperature hysteretic spin crossover in a new cyanoheterometallic framework.
2019
A new iron(II)-based spin-crossover compound with thermal hysteresis operating under ambient conditions is reported. This complex exhibits a high reproducibility of the spin transition in many successive thermal cycles, stability of both spin states at room temperature and an attractive operational temperature range.
EPR Studies of Atomic Impurities in Rare Gas Matrices
2003
In this article we give an overview of the matrix isolation technique combined with electron paramagnetic resonance (EPR) detection for embedded atomic impurities in solid rare gases. A special emphasis is put on impurity – matrix coupling effects combining both experimental and theoretical approaches.
Anharmonicity-induced polaron relaxation in GaAs/InAs quantum dots
2002
The anharmonicity-induced relaxation of a polaron in a quantum dot is analyzed using the Davydov diagonalization method, including the coherent renormalization of the relevant third-order phonon interaction. The resulting relaxation time for a small GaAs/InAs self-assembled quantum dot turns out to be a few times longer than that found previously by a perturbative method.
Dialysis of flavour compounds: Yields of extraction on model solution
1993
The extraction of 58 flavour compounds by Nafion membrane dialysis was studied using a model solution. Reproducibility and yield of the method were investigated. The coefficient of variation of the extraction yield was less than 15% for 48 of the 58 compounds tested. When the number of carbon atoms increased, the extraction yield fell to zero for compounds with more than ten carbon atoms. Flavour compounds with a cyclic structure showed a better diffusion rate through the membrane than other compounds with the same number of carbon atoms. The extraction yield seems to be correlated mainly to the hydrophobicity of the molecule. The use of the method for quantitative analysis was studied. Ext…
Topological magneto-optical effects and their quantization in noncoplanar antiferromagnets
2018
Reflecting the fundamental interactions of polarized light with magnetic matter, magneto-optical effects are well known since more than a century. The emergence of these phenomena is commonly attributed to the interplay between exchange splitting and spin-orbit coupling in the electronic structure of magnets. Using theoretical arguments, we demonstrate that topological magneto-optical effects can arise in noncoplanar antiferromagnets due to the finite scalar spin chirality, without any reference to exchange splitting or spin-orbit coupling. We propose spectral integrals of certain magneto-optical quantities that uncover the unique topological nature of the discovered effect. We also find th…
Stabilizing spin spirals and isolated skyrmions at low magnetic field exploiting vanishing magnetic anisotropy
2018
Skyrmions are topologically protected non-collinear magnetic structures. Their stability is ideally suited to carry information in, e.g., racetrack memories. The success of such a memory critically depends on the ability to stabilize and manipulate skyrmions at low magnetic fields. The non-collinear Dzyaloshinskii-Moriya interaction originating from spin-orbit coupling drives skyrmion formation. It competes with Heisenberg exchange and magnetic anisotropy favoring collinear states. Isolated skyrmions in ultra-thin films so far required magnetic fields as high as several Tesla. Here, we show that isolated skyrmions in a monolayer of Co/Ru(0001) can be stabilized down to vanishing fields. Eve…