A5052878789- Magnetic properties of thin films
- Magnetic Properties and Applications
- Magneto-Optical Properties and Applications
- Theoretical and Computational Physics
- Advanced Electron Microscopy Techniques and Applications
- Geomagnetism and Paleomagnetism Studies
- Advanced X-ray Imaging Techniques
- Magnetism in coordination complexes
- X-ray Spectroscopy and Fluorescence Analysis
- Characterization and Applications of Magnetic Nanoparticles
- Photonic and Optical Devices
- Magnetic Properties of Alloys
- Quantum and electron transport phenomena
- Magnetic and transport properties of perovskites and related materials
- Advanced Biosensing Techniques and Applications
- Advanced Memory and Neural Computing
- Organic and Molecular Conductors Research
- Physics of Superconductivity and Magnetism
- Nuclear Physics and Applications
- Advanced Fiber Optic Sensors
- Mechanical and Optical Resonators
- Crystallography and Radiation Phenomena
- Advanced Chemical Physics Studies
- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
Deutsches Elektronen-Synchrotron DESY
2008-2023
ETH Zurich
2000-2020
FHNW University of Applied Sciences and Arts
2020
Helmholtz-Zentrum Berlin für Materialien und Energie
2009-2015
University of Münster
2007
Universität Hamburg
2007
Stanford Synchrotron Radiation Lightsource
2001-2005
SLAC National Accelerator Laboratory
2005
Stanford University
2001
École Polytechnique Fédérale de Lausanne
1990-1998
A chemical and magnetic characterization of ferromagnet/antiferromagnet interfaces is essential to understand the microscopic origins exchange anisotropy other phenomena. We have used high-resolution L-edge x-ray absorption spectroscopy (XAS), which element specific sensitive environment spin orientation, investigate interface antiferromagnetic oxides with ferromagnetic metals. Clear quantitative evidence oxidation/reduction reactions at as-grown metal/oxide presented. In situ-- ex...
Using x-ray absorption spectromicroscopy we have imaged the uncompensated spins induced at surface of antiferromagnetic (AFM) NiO(100) by deposition ferromagnetic (FM) Co. These align parallel to AFM in and FM The interfacial arise from an ultrathin CoNiOx layer that is formed upon Co through reduction NiO surface. Ni are discussed terms "uncompensated spins" AFM/FM interfaces long held responsible for coercivity increases exchange bias. We find a direct correlation between their number size...
Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent moment of 4f electrons in ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast time 750 fs identical both systems slower times differ sizeably 40 ps 8 Tb. conclude that coupling electronically excited state is enhanced up 50 compared equilibrium.
Here we report the measurement of interfacial spin accumulation induced by Hall effect in Pt and W thin films using magneto-optical Kerr microscopy. We show that rotation has opposite sign scales linearly with current density. By comparing experimental results ab-initio calculations effects, quantitatively determine current-induced at interface as $5*10^{-12} \mu_B$A$^{-1}$cm$^2$ per atom. From thickness-dependent measurements, diffusion length a single film to be $11 \pm 3$ nm, which is...
Controlling magnetic order on ultrashort timescales is crucial for engineering the next-generation devices that combine ultrafast data processing with ultrahigh-density storage. An appealing scenario in this context use of femtosecond (fs) laser pulses as an ultrafast, external stimulus to fully set orientation and magnetization magnitude a spin ensemble. Achieving such control timescales, e.g., comparable excitation event itself, remains however challenge due lack understanding dynamical...
Single two-dimensional (2D) atomically thick magnetic particles of cobalt and iron with variable size shape were fabricated by combining a mask technique standard molecular beam epitaxy. Reduction the lateral in-plane magnetized 2D films down to about 100 nanometers did not essentially modify their properties; although separation boundaries decreased greatly, neither domain penetrated particle, nor was any sizable anisotropy observed. The mutual interaction negligible, state single particle...
Here the major upgrades of femtoslicing facility at BESSY II (Khan et al., 2006) are reviewed, giving a tutorial on how elliptical-polarized ultrashort soft X-ray pulses from electron storage rings generated high repetition rates. Employing 6 kHz femtosecond-laser system consisting two amplifiers that seeded by one Ti:Sa oscillator, total average flux photons 100 fs duration (FWHM) has been increased factor 120 to up 10(6) s(-1) (0.1% bandwidth)(-1) sample in range 250 1400 eV. Thanks new...
The phase transition from antiferromagnetic to ferromagnetic ordering in FeRh is investigated an element specific way by means of x-ray absorption spectroscopy. Dichroism sum rules allow us determine spin and orbital moments the two elements as system driven through transition. Increasing temperature 300 450 K, magnetic Fe Rh both evolve zero their final value, while ratio stays constant. Our experimental findings are supported results fully relativistic ab initio calculations.
Ultrafast magnetization dynamics triggered by femtosecond laser excitation of the FeRh alloy is investigated time-resolved x-ray magnetic circular dichroism. We measure a gradual growth within $\ensuremath{\approx}100\text{ }\text{ps}$ for both Fe and Rh elements as system laser-driven through its first-order phase transition from antiferromagnetic (AFM) to ferromagnetic (FM) state. A dynamic AFM-FM coexistence observed, identifying mechanism rapid nucleation subsequent slow expansion FM...
We follow for the first time evolution of spin and orbital angular momentum a thin Ni film during ultrafast demagnetization, by means x-ray magnetic circular dichroism. Both components decrease with 130 +/- 40 fs constant upon excitation femtosecond laser pulse. Additional absorption measurements reveal an increase in spin-orbit interaction 6 2 % this process. This is experimental demonstration quantifying importance mediated processes demagnetization.
Ultrafast magnetization dynamics induced by femtosecond laser pulses have been measured in ferrimagnetic Co${}_{0.8}$Gd${}_{0.2}$, Co${}_{0.74}$Tb${}_{0.26}$, and Co${}_{0.86}$Tb${}_{0.14}$ alloys. Using element sensitivity of x-ray magnetic circular dichroism at the Co ${L}_{3}$, Tb ${M}_{5}$, Gd ${M}_{5}$ edges, we see that demagnetization is dependent. We show a thermalization time as fast 280 $\ifmmode\pm\else\textpm\fi{}$ 30 fs observed for rare earth alloy when excited-state...
We have imaged the stripe domain structure of perpendicularly magnetized fcc ultrathin Fe films grown on Cu(100). The phase has a strong local orientational order and sustains two kinds fluctuations predicted by Abanov et al. [Phys. Rev. B 51, 1023 (1995)]: meandering dislocations. Before reaching Curie temperature, stripes transform into new so far unobserved structure, characterized domains with predominantly square corners. argue that this is tetragonal liquid proposed to separate from...
After excitation by femtosecond laser pulses, Gd and Tb exhibit ultrafast demagnetization in two steps, with the time constant of second step linked to coupling strength $4f$ magnetic moments lattice. In time-resolved magneto-optical Kerr effect measurements ${\mathrm{Gd}}_{1\ensuremath{-}x}{\mathrm{Tb}}_{x}$ alloys, we observe a decrease this from 33 9 ps content $x$ increasing 0 0.7. We explain behavior stronger spin-lattice compared Gd, which increases effective $x$. contrast, faster...
The magnetization dynamics of CoPd films excited by circularly polarized ultrashort laser pulses is studied time-resolved x-ray magnetic circular dichroism. In those the ultrafast measured at Co-${L}_{3}$ edge strongly sensitive to orbital moment $L$${}_{z}$. amount angular momentum transferred ferromagnetic evaluated $\ifmmode\pm\else\textpm\fi{}$0.1 $\ensuremath{\hbar}$/atom, which above detection limit experiment. Despite this, no polarization-dependent difference on could be evidenced....