A5007498672- Magnetic properties of thin films
- Theoretical and Computational Physics
- Magnetic Properties and Applications
- Characterization and Applications of Magnetic Nanoparticles
- Magnetic Properties of Alloys
- Physics of Superconductivity and Magnetism
- Advanced Thermodynamics and Statistical Mechanics
- Magnetic Properties and Synthesis of Ferrites
- Quantum and electron transport phenomena
- Electromagnetic Scattering and Analysis
- stochastic dynamics and bifurcation
- Spectroscopy and Quantum Chemical Studies
- Multiferroics and related materials
- Nuclear Physics and Applications
- Magneto-Optical Properties and Applications
- Metamaterials and Metasurfaces Applications
- Geomagnetism and Paleomagnetism Studies
- ZnO doping and properties
- Electromagnetic Simulation and Numerical Methods
- Microstructure and mechanical properties
- Microstructure and Mechanical Properties of Steels
- Metallurgical Processes and Thermodynamics
- advanced mathematical theories
- Flow Measurement and Analysis
- Advanced Electron Microscopy Techniques and Applications
General Numerics Research Lab
2018-2024
Innovent
2002-2013
Friedrich Schiller University Jena
1999
Helmholtz Institute Jena
1999
Leibniz Institute of Photonic Technology
1998
Schiller International University
1998
Friedrich-Alexander-Universität Erlangen-Nürnberg
1995
We show experimentally and by model calculations that in finite, nonellipsoidal, micrometer size magnetic thin film elements the dynamic eigenexcitations (spin waves) may exhibit strong spatial localization. This localization is due to formation of a potential well for spin waves highly inhomogeneous internal field within element.
A Brillouin light scattering study and theoretical interpretation of spin-wave modes in arrays in-plane magnetized micron-size rectangular ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ elements are reported. It is shown that two-dimensional eigenmodes these can be approximately described as products one-dimensional longitudinally transversely long finite-width permalloy stripes. The lowest dipole-exchange nature localized near the element edges, while higher a mostly dipolar weakly center....
We present spectral measurements of spin-wave excitations driven by direct spin-polarized current in a free layer nanoscale ${\mathrm{Ir}}_{20}{\mathrm{Mn}}_{80}∕{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}∕\mathrm{Cu}∕{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ spin valves. The reveal that large-amplitude coherent modes are excited over wide range bias current. frequency these exhibits series jumps as function due to transitions between different localized nonlinear the...
In this paper a detailed numerical study (in frames of the Slonczewski formalism) magnetization oscillations driven by spin-polarized current through thin elliptical nanoelement is presented. We show that sophisticated micromagnetic model, where polycrystalline structure taken into account, can explain qualitatively all most important features oscillation spectra recently observed experimentally (S.I. Kiselev et al., Nature, vol. 425, p. 380 (2003), namely: existence several equidistant...
We demonstrate (using full-scale micromagnetic simulations) that the spin injection driven steady-state precession of a thin magnetic nanoelement exhibit complicate transition from quasi-macrospin to chaotic behaviour with increasing element size. For parameters typical for those used experimentally we have found macrospin approximation becomes invalid already very small sizes (~ 30 nm), in contrast previously reported results (Li and Zhang, Phys. Rev. B, vol. B68, 024404-1 (2003))
This paper is devoted to numerical simulations of the magnetization dynamics driven by a spin-polarized current in extended ferromagnetic multilayers when point-contact setup used. We present (i) detailed analysis methodological problems arising such and (ii) physical results obtained on system similar that studied Rippard et al. [Phys. Rev. Lett. 92, 027201 (2004)]. demonstrate usage standard Slonczewski formalism for phenomenological treatment spin-induced torque leads qualitative...
We present numerical simulation studies of the steady-state magnetization dynamics driven by a spin-polarized current in point-contact geometry for case relatively large contact diameter $({D}_{\text{c}}=80\text{ }\text{nm})$ and small external field $(H=30\text{ }\text{Oe})$. show that under these conditions is qualitatively different from observed contacts fields. In particular, ``bullet'' mode with homogeneous core, which was dominating localized contacts, not found here. Instead, all...
A new methodology for micromagnetic simulations of magnetic nanocomposites is presented. The especially suitable two-phase composites consisting magnetically hard inclusions in a soft matrix phase. proposed technique allows us to avoid unnecessary discretization the ``hard'' (these are normally single-domain state) but enables arbitrary fine ``soft'' method applied determination equilibrium magnetization state an iron-based nanocomposite from Nanoperm (FeZrBCu) family alloys and calculation...
Using the Langevin dynamics, we have calculated numerically temperature and concentration dependence of complex alternating-current susceptibility χ(ω,T) for disordered systems fine magnetic particles taking into account dipolar interparticle interaction. We demonstrate that behaviour dependencies with increasing particle (which means interaction strength) frequency depends qualitatively on single-particle anisotropy damping parameter used in corresponding equation.
We present a method of calculation the effective magnetic permeability magnonic metamaterials containing arrays inclusions arbitrary shapes. The fully takes into account spectrum spin waves confined in inclusions. evaluate by considering particular case metamaterial formed stack identical two-dimensional (2D) periodic hexagonal disk-shaped nonmagnetic matrix. Two versions are considered. first approach is based on simple semianalytical theory that uses numerically calculated susceptibility...
In this paper we present a model which allows numerical studies of ferrofluid dynamics taking into account the internal magnetic degrees freedom particles. standard models moment particle is supposed to be fixed with respect itself, corresponds limit an infinitely high single-particle anisotropy. contrast strongly simplifying assumption, take that in real ferrofluids moments particles are allowed rotate themselves. Our results system equations motion describing both and mechanical freedom,...
We report a combined experimental and theoretical study of the quasistatic hysteresis dynamic excitations in large-area arrays NiFe nanodisks forming hexagonal lattice with constant 390 nm. Arrays were fabricated by patterning 20-nm-thick film using etched nanosphere lithography. have studied close-packed (edge-to-edge separation between disks ${d}_{\mathrm{cp}}$ $=$ 65 nm) an ultraclosed packed (${d}_{\mathrm{ucp}}$ 20 array. Hysteresis loops for both qualitatively similar nearly isotropic,...
We have developed a method that enables fast and exact evaluation of the long-range interaction field by simulating lattice dipolar systems with periodic boundary conditions. The is based on combination fast-Fourier-transformation technique modified Ewald for sum calculation. used our algorithm simulations quasistatic remagnetization processes in two-dimensional hexagonal lattices dipoles uniaxial on-site anisotropy (anisotropic Heisenberg model interaction), which can be considered as...
In this paper, we study magnetization excitations induced in a thin extended film by spin-polarized dc current injected through point contact the current-perpendicular-to-plane geometry. Using full-scale micromagnetic simulations, demonstrate that addition to oscillations of propagating wave type, there exist also two localized oscillation modes. The first mode has relatively homogeneous structure its core and corresponds so-called ``bullet'' predicted analytically Slavin Tiberkevich [Phys....
We have used numerical micromagnetics for the calculation of magnetic (small-angle) neutron scattering cross section $d{\ensuremath{\Sigma}}_{M}/d\ensuremath{\Omega}$ nanocomposites. In contrast to experiments, in which one generally measures only a weighted sum Fourier components magnetization, our approach allows study behavior individual contributions $d{\ensuremath{\Sigma}}_{M}/d\ensuremath{\Omega}$. The procedure furnishes unique and fundamental information regarding microstructure...
We demonstrate that the Ito and Stratonovich stochastic calculus lead to identical results when applied dynamics study of magnetic systems consisting dipoles with constant magnitude, despite multiplicative noise appearing in corresponding Langevin equations. The immediate consequence this statement is any numerical method used for solution these equations will physically correct results.
In this paper, we present an overview of recent progress made in understanding the spin-torque induced magnetization dynamics nanodevices using mesoscopic micromagnetic simulations. first part, perform a detailed quantitative comparison between numerical modelling and experimental data obtained on nanopillar devices. Here show that although many qualitative features observed can be satisfactorily explained by full-scale models, our experiments is still far from being complete. This manifests...
We present a new micromagnetic methodology for numerical simulations of magnetic nanocomposites. The is especially suitable simulating two-phase systems consisting magnetically “hard” inclusions in “soft” phase, because it avoids the unnecessary discretization inclusions, allowing simultaneously an arbitrary fine phase. As application example this novel concept we have calculated equilibrium magnetization distribution iron-based nanocomposite Fe-Zr-B-Cu (Nanoperm) and corresponding...
Here, the authors address one of most important problems statistical physics in magnetism -- evaluation escape rate over high energy barriers using archetypal example a biaxial macrospin. After deriving an analytical expression for corresponding rate, predictions two and four numerical methods switching time dependence on barrier height range 10--60 kT (so that spans 20 orders magnitude) are compared. It is shown large only forward flux method provides physically reasonable results.