A5053174048- Magnetic properties of thin films
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Topological Materials and Phenomena
- 2D Materials and Applications
- X-ray Diffraction in Crystallography
- Graphene research and applications
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- ZnO doping and properties
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Theoretical and Computational Physics
- Molecular Junctions and Nanostructures
- Surface Chemistry and Catalysis
- Copper-based nanomaterials and applications
- Quasicrystal Structures and Properties
- Semiconductor materials and devices
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- Electron and X-Ray Spectroscopy Techniques
- Paleontology and Evolutionary Biology
- Crystal Structures and Properties
- Iron-based superconductors research
Max Planck Institute of Microstructure Physics
2015-2024
Martin Luther University Halle-Wittenberg
2019
Max Planck Society
2004-2014
Technical University of Darmstadt
2010
Ludwig-Maximilians-Universität München
1992-2003
Crystal Research (United States)
1993
Deutsches Elektronen-Synchrotron DESY
1990-1991
Freie Universität Berlin
1989-1991
Siemens (Germany)
1991
A novel nonpolar structure of 2 monolayer (ML) thick ZnO(0001) films grown on Ag(111) has been revealed, using surface x-ray diffraction and scanning tunneling microscopy. Zn O atoms are arranged in planar sheets like the hexagonal boron-nitride prototype structure. The observed depolarization is accompanied by a significant lateral 1.6% expansion lattice parameter 3% reduced Zn-O bond length within sheets. stabilizes an atomically flat morphology unseen for ZnO surfaces thus far. transition...
The geometric structure of MgO deposited on Fe(001) in ultrahigh vacuum by electron evaporation was determined detail using surface x-ray diffraction. In contrast to the common belief that grows direct contact substrate, we find an FeO interface layer between substrate and growing which has not been considered thus far. This result opens new perspectives for understanding Fe/MgO/Fe(001) tunneling magnetoresistance effect general.
Single-crystalline ${\mathrm{Co}}_{2}\mathrm{MnSi}$ Heusler alloy films have been grown on GaAs(001) substrates by pulsed laser deposition (PLD). The best crystallographic quality of the has achieved after at 450 K. exhibit in-plane uniaxial magnetic anisotropy with easy axis magnetization along [1-10] direction superimposed a fourfold ⟨110⟩. Spin-resolved photoemission measurements single-crystalline reveal spin-resolved density states that is in qualitative agreement recent band structure...
Using ab initio thermodynamics we compile a phase diagram for the surface of Fe3O4(001) as function temperature and oxygen pressures. A hitherto ignored polar termination with octahedral iron forming wave-like structure along [110]-direction is identified lowest energy configuration over broad range gas-phase conditions. This novel geometry confirmed in x-ray diffraction analysis. The stabilization Fe3O4(001)-surface goes together dramatic changes electronic magnetic properties, e.g.,...
There is considerable interest in van der Waals (vdW) materials as potential hosts for chiral skyrmionic spin textures. Of particular the ferromagnetic, metallic compound Fe
Transition-metal dichalcogenides intercalated with 3d-transition metals within the van der Waals (vdW) gaps have been focus of intense investigations owing to their fascinating structural and magnetic properties. At certain concentrations atoms form ordered superstructures that exhibit ferromagnetic or anti-ferromagnetic ordering. Here we show self-intercalated compound Cr1+δTe2 δ ≈ 0.3 exhibits a new, so far unseen, three-dimensionally (2×2×2) superstructure. Furthermore, high resolution...
The current-induced spin-orbit torque switching of ferromagnets has had huge impact in spintronics. However, short spin-diffusion lengths limit the thickness switchable ferromagnetic layers, thereby limiting their thermal stability. Here, we report a previously unobserved seeded (SSOT) by which current can set magnetic states even thick layers chiral kagome antiferromagnet Mn3Sn. mechanism involves setting orientation antiferromagnetic domains thin region at interface with spin currents...
Oxygen defects and their atomic arrangements play a significant role in the physical properties of many transition metal oxides. The exemplary perovskite SrCoO3-δ (P-SCO) is metallic ferromagnetic. However, its daughter phase, brownmillerite SrCoO2.5 (BM-SCO), insulating an antiferromagnet. Moreover, BM-SCO exhibits oxygen vacancy channels (OVCs) that thin films can be oriented either horizontally (H-SCO) or vertically (V-SCO) to film's surface. To date, orientation these OVCs has been...
The niobium oxide polymorph T-Nb2O5 has been extensively investigated in its bulk form especially for applications fast-charging batteries and electrochemical (pseudo)capacitors. Its crystal structure that two-dimensional (2D) layers with very low steric hindrance allows fast Li-ion migration. However, since discovery 1941, the growth of single-crystalline thin films electronic have not yet realized, likely due to large orthorhombic unit cell along existence many polymorphs. Here we...
The generation of spin currents and their application to the manipulation magnetic states is fundamental spintronics. Of particular interest are chiral antiferromagnets that exhibit properties typical ferromagnetic materials even though they have negligible magnetization. Here, we report a robust current with both in-plane out-of-plane polarization in epitaxial thin films antiferromagnet Mn3Sn proximity permalloy layers. By employing temperature-dependent spin-torque resonance, find...
We present an experimental and theoretical study of the geometric structure ultrathin BaTiO(3) films grown on Fe(001). Surface x-ray diffraction reveals that are terminated by a BaO layer, while TiO(2) layer is next to top Fe layer. Cations in termination layers have incomplete oxygen shells inducing strong vertical relaxations. Onset polarization observed at minimum thickness two unit cells. Our findings supported first-principles calculations providing quantitative insight into...
The proximity-coupling of a chiral non-collinear antiferromagnet (AFM)1-5 with singlet superconductor allows spin-unpolarized Cooper pairs to be converted into spin-polarized triplet pairs6-8, thereby enabling non-dissipative, long-range spin correlations9-14. mechanism this conversion derives from fictitious magnetic fields that are created by non-zero Berry phase15 in AFMs atomic-scale arrangements1-5. Here we report long-ranged lateral Josephson supercurrents through an epitaxial thin...
Cr(1+δ)Te2 are pseudo-layered compounds consisting of CrTe2 transition metal dichalcogenide (TMD) layers with additional (δ) self-intercalated Cr atoms. The recent search for ferromagnetic 2D materials revived the interest into chromium tellurides. Here, nanolayers epitaxially grown on MoS2 (0001), forming prototypical van der Waals heterostructures. Under optimized growth conditions, ultrathin films only two TMD a single intercalated Cr-layer achieved, sheet surfaces. Detailed compositional...
Antiferromagnets with non-collinear spin structures display various properties that make them attractive for spintronic devices. Some of the most interesting examples are an anomalous Hall effect despite negligible magnetization and a unusual polarization directions. However, these effects can only be observed when sample is set predominantly into single antiferromagnetic domain state. This achieved compensated structure perturbed displays weak moments due to canting allows external control....
We present x-ray diffraction experiments and multiple-scattering calculations on the structure transport properties of a Fe/MgO/Fe(001) magnetic tunnel junction (MTJ). Coherent growth top Fe electrode MgO spacer is observed only for deposition in ambient oxygen atmosphere leading to coherent symmetric MTJ characterized by FeO layers at both interfaces. This goes parallel with indicating large positive magnetoresistance (TMR) values such junctions. The results have important implications...
Using surface x-ray diffraction we have investigated the geometric structure of interface between thermally grown MgO layers and Fe(001). The MgO/Fe(001) is part Fe/MgO/Fe junction, which has become a prototype system in study tunneling-magnetoresistance (TMR) effect. For all samples studied coverage range about 0.35 4.6 ML find clear evidence for presence substoichiometric FeO layer bulk Fe crystal adlayers. partial oxidation Fe(001) takes place during deposition first monolayer approaches...
Over the past decade family of chiral noncollinear spin textures has continued to expand with observation in metallic compounds Bloch-like skyrmions several B20 compounds, and antiskyrmions a tetragonal inverse Heusler. Néel like bulk crystals broken inversion symmetry have recently been seen two distinct nonmetallic GaV4 S8 VOSe2 O5 at low temperatures (below ≈13 K) only. Here, first compound PtMnGa and, moreover, high up ≈220 K is reported. Lorentz transmission electron microscopy reveals...
Spin-triplet supercurrent spin valves are of practical importance for the realization superconducting spintronic logic circuits. In ferromagnetic Josephson junctions, magnetic-field-controlled non-collinearity between spin-mixer and spin-rotator magnetizations switches spin-polarized triplet supercurrents on off. Here we report an antiferromagnetic equivalent such spin-triplet in chiral junctions as well a direct-current quantum interference device. We employ topological antiferromagnet...
A conducting 2D electron gas (2DEG) is formed at the interface between epitaxial LaFeO3 layers >3 unit cells thick and surface of SrTiO3 single crystals. The 2DEG exquisitely sensitive to cation intermixing oxygen nonstoichiometry. It shown that latter thus allows controllable formation via ionic liquid gating, thereby forming a nonvolatile switch. As service our authors readers, this journal provides supporting information supplied by authors. Such materials are peer reviewed may be...
Angular resolved photoemission spectroscopy in combination with ab initio calculations show that trace amounts of carbon doping the Bi_{2}Se_{3} surface allows controlled shift Dirac point within bulk band gap. In contrast to expectation, no Rashba-split two-dimensional electron gas states appear. This unique electronic modification is related structural characterized by an expansion top Se-Bi spacing ≈11% as evidenced x-ray diffraction. Our results provide new ways tune structure...
We report on the first observation of an approximant structure to recently discovered two-dimensional oxide quasicrystal. Using scanning tunneling microscopy, low-energy electron diffraction, and surface x-ray diffraction in combination with ab initio calculations, atomic bonding scheme are determined. The follows a 3^{2}.4.3.4 Archimedean tiling. Ti atoms reside at corners each tiling element threefold coordinated oxygen atoms. Ba separate TiO_{3} clusters, leading fundamental edge length 6.7 Å.
Using soft-x-ray resonant magnetic scattering in combination with first-principles calculations for noncollinear configurations we present a new model of the magnetism ultrathin fcc Fe films on Cu(001). We find presence blocks robust structure, while relative directions moments different are sensitive to detailed atomic structure and temperature. The noncollinearity is directly demonstrated, which has not been possible so far.