A5011242091- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Molecular Junctions and Nanostructures
- Electron and X-Ray Spectroscopy Techniques
- Magnetism in coordination complexes
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Electronic and Structural Properties of Oxides
- Porphyrin and Phthalocyanine Chemistry
- Graphene research and applications
- Advanced Materials Characterization Techniques
- Multiferroics and related materials
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- Topological Materials and Phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Cold Atom Physics and Bose-Einstein Condensates
- Ga2O3 and related materials
- Nuclear Physics and Applications
- Quantum optics and atomic interactions
- Surface Chemistry and Catalysis
- Boron and Carbon Nanomaterials Research
RWTH Aachen University
2021-2024
Karlsruhe Institute of Technology
2011-2022
Institut Català de Nanociència i Nanotecnologia
2010-2014
Institute for Theoretical and Experimental Physics
2006
Max Planck Institute of Microstructure Physics
2006
We investigate the interaction of TbPc(2) single molecule magnets (SMMs) with ferromagnetic Ni substrates. Using element-resolved x-ray magnetic circular dichroism, we show that couples antiferromagnetically to films through ligand-mediated superexchange. This coupling is strongly anisotropic and can be manipulated by doping interface electron acceptor or donor atoms. observe relative orientation substrate anisotropy axes critically affects SMM behavior. complexes deposited on...
The recently discovered giant magnetic anisotropy of single Co atoms raises the hope storage in small clusters. We present a joint experimental and theoretical study spin dynamics Fe atoms, dimers, trimers on Pt(111). Giant anisotropies individual clusters as well lifetimes excited states were determined with inelastic scanning tunneling spectroscopy. short due to hybridization-induced electron-electron scattering oppose stability provided by anisotropies.
Abstract 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 stabilize and manipulate skyrmions at low fields. Dzyaloshinskii-Moriya interaction originating from spin-orbit coupling drives skyrmion formation. It competes with Heisenberg exchange anisotropy favoring collinear states. Isolated in ultra-thin films so far...
Using spin-polarized scanning tunneling microscopy, the local excitation of magnons in Fe and Co has been studied. A large cross section for magnon was found bulk samples while thin films on Cu(111) linearly scales with film thickness. Recording inelastic spectra coated W tips a magnetic field, magnonic nature proven. Magnon could be detected without use separating insulating layer opening up possibility to directly study nanostructures via currents.
We investigate the possibility to induce exchange bias between single molecule magnets (SMM) and metallic or oxide antiferromagnetic substrates. Element-resolved X-ray magnetic circular dichroism measurements reveal, respectively, presence absence of unidirectional anisotropy for TbPc(2) SMM deposited on Mn CoO layers. thin films present hysteresis a negative horizontal shift Tb magnetization loop after field cooling, consistent with observation pinned spins in layer coupled parallel moment....
Abstract Nanomagnets of controlled size, organized into regular patterns open new perspectives in the fields nanoelectronics, spintronics, and quantum computation. Self‐assembling processes on various types substrates allow designing fine‐structured architectures tuning their magnetic properties. Here, starting from a description fundamental interactions at nanoscale, we review recent experimental approaches to fabricate zero‐, one‐, two‐dimensional particle arrays with dimensions reduced...
A combined experimental and theoretical study on the inelastic transfer of spin momentum between a spin-polarized tunneling current ferromagnetic electrode is presented. Using spectroscopy across vacuum gap at 4 K we show that high-energy magnons are efficiently excited in inelastic-scattering events asymmetry magnon excitation for into out ferromagnet proportional to polarization current. We discuss size resulting torque explain energy distribution basis scattering mediated by itinerant...
Using low-temperature scanning tunneling microscopy, electron transport across single ${\text{H}}_{2}$- or Co-phthalocyanine molecules was studied. The were adsorbed onto clean Cu(111) surface and Co nanostructures on contacted through a controlled approach of the tip. Soft phonons from molecular side groups promote discrete jump to contact followed by bond formation. Molecular conductances strongly depend substrate but not central atom molecules. This is explained charge transfer...
We investigate the scattering of surface electrons by edges graphene islands grown on Ni(111). By combining local tunneling spectroscopy and ab initio electronic structure calculations we find that hybridization between Ni states results in strongly reflecting edges. Quantum interference patterns formed around reveal a spin-dependent Shockley bands Ni, which attribute to their distinct coupling bulk states. Moreover, strong dependence amplitude atomic edges, depending orbital character energy
We have designed and built a scanning tunneling microscope (STM) setup for operation at millikelvin temperatures in an ultrahigh vacuum. A compact cryostat with integrated dilution refrigerator has been that allows measurements base temperature of 25 mK the magnetic field up to 7.5 T low mechanical electronic noise. The is not larger than conventional helium bath cryostats (23 13 l nitrogen helium, respectively) so does require large experimental hall fits easily into standard lab space....
Although the dispersion of magnons has been measured in many bulk materials, few studies deal with changes when material is form a thin film, system that interest for applications. Here we review inelastic tunneling spectroscopy magnon Mn/Cu3Au(1 0 0) and present new on Co Ni films Cu(1 0). The Mn closely follows samples negligible dependence thickness. lifetime depends slightly film thickness, decreases considerably as energy increases. In Ni/Cu(1 thickness much more pronounced....
Undoped and slightly Eu-doped SmB6 samples show the opening of a gap with decreasing temperature below ~150 K. The spectral shapes near Fermi level (EF) at 15 K have shown marked increase in intensity peak binding energy (EB) approximately 12 meV photon (hν) from 17 to 7 eV. Angle-resolved spectra measured hν = 35 eV just after situ cleavage showed clear dispersions several bands EB region EF 4 Spin-polarized photoelectron were then light incidence angle ~50°. In contrast lack spin...
We study the anisotropy of spin and orbital magnetization ultrathin Co layers characterized by structure inversion asymmetry, namely Pt/Co/AlO${}_{x}$ trilayers with thicknesses between 0.6 2 nm. use x-ray magnetic circular dichroism (XMCD) to probe layer along two orthogonal measurement geometries. By combining transverse collinear XMCD, we achieve a vector moments. find an enhanced anisotropic moment localized at interface verify connection macroscopic trilayer. These results provide link...
High-resolution photoemission spectroscopy and realistic ab-initio calculations have been employed to analyze the onset progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by free-electron environment, Coulomb interaction among d-electrons gives rise complex electronic configurations. multiplet structure a single atom evolves gradually dissolves into quasiparticle peak near Fermi level with increasing host...
Dependence of the spectral functions near Fermi level on temperature and rare-earth atom doping was studied in detail for strongly correlated alloys Sm1−xEuxB6 Yb1−xLuxB12 by photoelectron spectroscopy at ∼8000 eV as well 7 8.4 eV. It found that 4f lattice coherence intrinsic gap are robust least up to Eu substitution x = 0.15 while both collapse Lu already 0.125 Yb1−xLuxB12. As dependence shapes low temperatures, rather contrasting results were observed between YbB12 SmB6. Although shape...
Investigations of single magnetic atoms on a Pt surface revealed giant anisotropies. Recently, scanning tunneling microscopy was used to probe Fe and Co atoms, dimers, trimers Pt(111). The anisotropy and, additionally, the lifetimes magnetically excited states were measured by inelastic spectroscopy. are in order femtoseconds due an effective electron-electron relaxation process caused strong hybridization impurity substrate. different explained quantum mechanical nature measurements dimer...
We present an efficient methodology to study spin waves in disordered materials. The approach is based on a Heisenberg model and enables calculations of magnon properties systems with disorder arbitrary kind concentration impurities. Disorder effects are taken into account within two complementary approaches. Magnons substitutional (uncorrelated) can be efficiently calculated single-site coherent potential approximation for the model. From computation point view method inexpensive directly...
We present a view on inelastic scanning tunneling spectroscopy of magnetic impurities relying states the total angular momentum $J=L+S$ in presence crystal field. show that selection rules for spin-flip scattering within $J$-multiplet agree with simple effective spin model, but also deviations from latter transition probabilities. A reinterpretation some recent experimental findings description based $J$ is done.
Due to underlying symmetries the ground states of magnetic adatoms may be highly stable, which opens perspectives for application as single-atom memory. A specific example is a single holmium atom (with $J=8$) on platinum (111) surface exceptionally long lifetimes were observed in recent scanning tunneling microscopy studies. For control and read-out must coupled electronic contacts. Hence spin dynamics system governed by quantum master equation. Our analysis shows that general it cannot...
Highly bulk-sensitive hard x-ray photoemission has been performed for the Magn\'eli phase ${\text{V}}_{5}{\text{O}}_{9}$ and ${\text{V}}_{6}{\text{O}}_{11}$, which are composed of ${\text{V}}_{2}{\text{O}}_{3}$ ${\text{VO}}_{2}$ from chemical point view. The valence-band spectra near Fermi level rather similar between ${\text{V}}_{6}{\text{O}}_{11}$ in both metallic insulating phases. Although core-level noticeably different. Our results understood by considering contribution V-V...
In this combined experimental and theoretical work, we report on the evolution of skyrmion radius its destruction in system Co/Ru(0001) when an out-of-plane magnetic field is applied. At low fields, skyrmions are metastable display elliptical instability which along short axis, spin texture approaches that spin-spiral phase long axis expands order to go back ground state. high observe round finite size up collapse Bc, where they destroyed topological charge annihilated. We estimate Bc via...