A5001207826- Magnetic properties of thin films
- Magnetic Properties and Applications
- High-pressure geophysics and materials
- Magnetic and transport properties of perovskites and related materials
- Force Microscopy Techniques and Applications
- Magneto-Optical Properties and Applications
- Laser Material Processing Techniques
- Theoretical and Computational Physics
- Advanced Chemical Physics Studies
- Thermal Expansion and Ionic Conductivity
- nanoparticles nucleation surface interactions
- Integrated Circuits and Semiconductor Failure Analysis
- Thermal properties of materials
- Rare-earth and actinide compounds
- Metal and Thin Film Mechanics
- Advanced Materials Characterization Techniques
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Advanced Electron Microscopy Techniques and Applications
- Surface Roughness and Optical Measurements
- Adhesion, Friction, and Surface Interactions
- Diamond and Carbon-based Materials Research
- Ultrasonics and Acoustic Wave Propagation
- Surface and Thin Film Phenomena
- Metallic Glasses and Amorphous Alloys
University of Potsdam
2020-2024
Max Planck Institute for Solid State Research
2021
Antiferromagnetic materials have been proposed as new types of narrowband THz spintronic devices owing to their ultrafast spin dynamics. Manipulating coherently dynamics, however, remains a key challenge that is envisioned be accomplished by spin-orbit torques or direct optical excitations. Here, we demonstrate the combined generation broadband (incoherent) magnons and (coherent) at 1 in low damping thin films NiO/Pt. We evidence, experimentally through modeling, two excitation processes...
We use ultrafast x-ray diffraction and the polar time-resolved magneto-optical Kerr effect to study laser-induced metamagnetic phase transition in two FeRh films with thicknesses below above optical penetration depth. In thin film, we identify an intrinsic timescale for light-induced nucleation of ferromagnetic (FM) domains antiferromagnetic material 8ps, which is substantially longer than time it takes strain waves traverse film. For inhomogeneously excited thicker only optically...
Abstract By ultrafast x‐ray diffraction (UXRD), it is shown that the laser‐induced magnetostructural phase transition in FeRh nanoislands proceeds faster and more complete than continuous films. An intrinsic 8 ps timescale observed for nucleation of ferromagnetic (FM) domains optically excited fraction both types samples. For film, substrate‐near regions are not directly exposed to light only slowly transformed FM state after heating above temperature via near‐equilibrium heat transport....
Abstract When the spatial dimensions of metallic heterostructures shrink below mean free path its conduction electrons, transport electrons and hence thermal energy by continuously changes from diffusive to ballistic. Electron–phonon coupling sets nanoscale time for equilibration electron lattice temperatures picosecond range. A particularly intriguing situation occurs in trilayer combining metals with very different electron–phonon strength: Heat deposited few atomic layers Pt is...
Using time-resolved x-ray diffraction, we demonstrate the manipulation of picosecond strain response a metallic heterostructure consisting dysprosium (Dy) transducer and niobium (Nb) detection layer by an external magnetic field. We utilize first-order ferromagnetic–antiferromagnetic phase transition Dy layer, which provides additional large contractive stress upon laser excitation compared to its zero-field response. This enhances laser-induced contraction changes shape pulses driven in...
We study the ultrafast electronic transport of energy in a photoexcited nanoscale Au/Fe hetero-structure by modeling spatiotemporal profile densities that drives transient strain, which we quantify femtosecond x-ray diffraction. This flow is relevant for intrinsic demagnetization and spin transport. measured lattice strain different Fe layer thicknesses ranging from few atomic layers to several nanometers modeled densities. The combination high electron-phonon coupling coefficient large...
We demonstrate the coherent optical control of magnetization precession in a thin Ni film by second excitation pulse, which amplifies or attenuates induced first pulse depending on fluences pump-pulses and pump-pump delay. This goes beyond conventional strategy, where same mechanism drives in-phase out-of-phase. balance magneto-acoustic driven quasi-static strain shape-anisotropy change triggered laser-induced demagnetization. These mechanisms tilt transient effective magnetic field opposite...
Optical excitation of spin-ordered rare earth metals triggers a complex response the crystal lattice since expansive stresses from electron and phonon excitations compete with contractive stress induced by spin disorder. Using ultrafast x-ray diffraction experiments, we study layer specific strain dysprosium film within metallic heterostructure upon femtosecond laser-excitation. The elastic diffusive transport energy to an adjacent, non-excited detection clearly separates contributions...
An experimental technique that allows faster assessment of out-of-plane strain dynamics thin film heterostructures via x-ray diffraction is presented. In contrast to conventional high-speed reciprocal space-mapping setups, our approach reduces the measurement time drastically due a fixed geometry with position-sensitive detector. This means neither incident (ω) nor exit (2θ) angle scanned during diffraction. Shifts peaks on area detector originate from an within sample. Quantitative requires...
We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving picosecond strain response a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. exemplify how anisotropic bulk equilibrium thermal expansion can be used predict deposition energy. It is key consider that laterally homogeneous excitation changes compared near-equilibrium because balanced in-plane stresses suppress Poisson on timescale. find very large...
Hafnium Nitride (HfN) is a promising and very robust alternative to gold for applications of nanoscale metals. Details the nanomorphology related variations in strain states optical properties can be crucial nanophotonics plasmon-assisted chemistry. We use ultrafast reciprocal space mapping (URSM) with hard x-rays unveil thin HfN films. Static high-resolution x-ray diffraction reveals twofold composition films being separated into regions identical lattice constant similar out-of-plane but...
Abstract Hafnium Nitride (HfN) is a promising and very robust alternative to gold for applications of nanoscale metals. Details the nanomorphology related variations in strain states optical properties can be crucial nanophotonics plasmon‐assisted chemistry. Ultrafast reciprocal space mapping (URSM) with hard X‐rays used unveil thin HfN films. Static high‐resolution X‐ray diffraction reveals twofold composition films being separated into regions identical lattice constant similar...
<title>Abstract</title> We use ultrafast x-ray diffraction to study non-equilibrium pathways of the phase transition in FeRh parametrized by structural response. By increasing pump-pulse duration beyond electron-phonon coupling time, we suppress present upon femtosecond laser excitation but still photoexcite electrons non-thermal states. Irrespective pump pulse duration, find an optically induced nucleation ferromagnetic domains on 8 ps timescale that starts as soon successively deposited...
We use ultrafast x-ray diffraction (UXRD) and the polar time-resolved magneto-optical Kerr effect (tr-MOKE) to study laser-induced metamagnetic phase transition in two FeRh films with thicknesses below above optical penetration depth. In thin film, we identify an intrinsic timescale for light-induced nucleation of ferromagnetic (FM) domains antiferromagnetic material $8\,\text{ps}$ that is substantially slower than speed sound. For inhomogeneously excited thicker only optically near-surface...
By ultrafast x-ray diffraction we show that the laser-induced magnetostructural phase transition in FeRh nanoislands proceeds faster and more complete than continuous films. We observe an intrinsic 8 ps timescale for nucleation of ferromagnetic (FM) domains both types samples. For film, substrate-near regions, which are not directly exposed to light, only slowly transformed FM state by domain wall motion following heat transport. In contrast, numerical modeling plasmonic absorption...
This review discusses picosecond ultrasonics experiments using ultrashort hard x-ray probe pulses to extract the transient strain response of laser-excited nanoscopic structures from Bragg-peak shifts. method provides direct, layer-specific, and quantitative information on for down few-nm thickness. We model elastic wave equation express driving stress Grüneisen parameters stating that laser-induced is proportional energy density changes in microscopic subsystems solid, i.e., electrons,...
We use ultrafast x-ray diffraction to examine the impact of an electron-phonon non-equilibrium on kinetics antiferromagnetic-to-ferromagnetic phase transition in FeRh parameterized by structural response. By increasing pump-pulse duration up $10.5\,\text{ps}$, we suppressed between electrons and phonons present upon femtosecond laser excitation. However, independently pump pulse duration, find a nucleation ferromagnetic domains $8\,\text{ps}$ timescale that starts as soon successively...
We experimentally demonstrate how nanoscale heterostructure design controls the effects of laser-induced heat and strain on magnetization precession. By introducing insulating MgO layers into metallic Pt-Cu-Ni heterostructures we block propagation hot electrons to control dynamics by tailoring spatio-temporal shape transient strain, which quantify ultrafast x-ray diffraction experiments. access corresponding precession in these using time-resolved magneto-optical Kerr effect polar geometry...
We demonstrate the coherent optical control of magnetization precession in a thin Ni film by second excitation pulse which amplifies or attenuates induced first depending on fluences pump-pulses and pump-pump delay. This goes beyond conventional strategy, where same mechanism drives out-of phase. balance magneto-acoustic driven quasi-static strain shape-anisotropy change triggered laser-induced demagnetization. These mechanisms tilt transient effective magnetic field opposite directions case...
In article number 2004555, Matias Bargheer and co-workers report ultrafast X-ray diffraction experiments on nanoscale metal heterostructures, which reveal counterintuitive heat transport consistent with diffusion including electron-phonon interaction. The energy deposited in few atomic layers of Pt is transported into a Ni film, heated more than the 100 nm Cu film through conducted.