A5103243609- Magnetic properties of thin films
- Magnetic Properties and Applications
- Theoretical and Computational Physics
- Quantum and electron transport phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Physics of Superconductivity and Magnetism
- Magneto-Optical Properties and Applications
- Nonlinear Dynamics and Pattern Formation
- stochastic dynamics and bifurcation
- Electromagnetic Simulation and Numerical Methods
- Advanced Thermodynamics and Statistical Mechanics
- Geomagnetism and Paleomagnetism Studies
- Non-Destructive Testing Techniques
- Piezoelectric Actuators and Control
- Force Microscopy Techniques and Applications
- Microstructure and Mechanical Properties of Steels
- Electric Motor Design and Analysis
- Magnetic confinement fusion research
- Neural Networks and Applications
- Quantum chaos and dynamical systems
- Quantum Mechanics and Non-Hermitian Physics
- Neural Networks and Reservoir Computing
- Advanced Memory and Neural Computing
- Magnetic Properties of Alloys
- Mechanical and Optical Resonators
University of Naples Federico II
2015-2024
Ingegneria dei Trasporti (Italy)
1999-2024
Elettra-Sincrotrone Trieste S.C.p.A.
2016-2017
Institute for Scientific Interchange
2011-2016
University of Maryland, College Park
1999-2012
University of Sheffield
2009
Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
2001-2004
A novel theoretical approach to magnetization dynamics driven by spin-polarized currents is presented. Complete stability diagrams are obtained for the case where spin torques and external magnetic fields simultaneously present. Quantitative predictions made critical inducing switching, amplitude frequency of self-oscillations, conditions leading hysteretic transitions between self-oscillations stationary states.
We have measured spin transfer-induced dynamics in magnetic nanocontact devices having a perpendicularly magnetized Co/Ni free layer and an in-plane CoFe fixed layer. The frequencies powers of the excitations agree well with predictions single-domain model indicate that excited correspond to precessional orbits angles ranging from zero 90 degrees as applied current is increased at field. From measurements onset function field strength we estimate magnitude torque asymmetry parameter lambda ~...
Exact analytical results are presented for the nonlinear large motion of magnetization vector in a body with uniaxial symmetry subject to circularly polarized field. The absence chaos, existence pure time-harmonic modes no generation higher-order harmonics, and quasiperiodic spontaneous breaking rotational proven. Application ferromagnetic resonance connection Stoner-Wohlfarth model discussed.
This paper deals with mathematical models of magnetic hysteresis implemented by assembling hysterons play and stop type. A procedure for the identification these is described, their behaviors are compared to experimental results. comparison Preisach Prandtl-Ishlinskii performed. It shown that Play-Type Model a possible alternative Preisach's algorithm, whereas Stop-Type apt represent inverse operator. Simulations adopting both reported data. Moreover, an application analysis ferroresonant...
We have numerically solved the Landau-Lifshitz-Gilbert (LLG) equation in its standard and inertial forms to study magnetization switching dynamics a $3d$ thin film ferromagnet. The is triggered by ultrashort magnetic field pulses of varying width amplitude picosecond Tesla range. compared solutions two equations terms characteristic, speed energy analysis. Both return qualitatively similar dynamics, characterized regions slower precessional behavior faster ballistic motion. In case found 25...
A general neural approach to magnetic hysteresis modeling is proposed. The memory storage properties of systems with rate independent are outlined. Thus, it shown how possible build a model based on feed-forward networks (NN's) which fulfills these properties. identification the consists in training NN's by usual algorithms such as backpropagation. Finally, proposed has been tested comparing its predictions experimental data.
Abstract The emergence of exceptional points (EPs) in the parameter space a non-hermitian (2D) eigenvalue problem has long been interest mathematical physics, however, only last decade entered scope experiments. In coupled systems, EPs give rise to unique physical phenomena, and enable development highly sensitive sensors. Here, we demonstrate at room temperature spintronic nanoscale oscillators exploit system’s non-hermiticity. We observe amplitude death self-oscillations other complex...
For pt.I see P. Thiran et al., ibid., vol.45, no.8, pp.777-89 (1998). This second of two papers studies how and when a global propagation information, introduced as initial condition, is possible through one-dimensional (1-D) Cellular Neural Network (CNN) with connections between nearest neighbors only. We will focus on circular arrays, which have the most regular structure, we show that periodic solutions exist, compute one them analytically. also study their stability.
The implicit midpoint time-integration technique is applied to the stochastic Landau-Lifshitz-Gilbert (LLG) equation. numerical scheme converges Stratonovich solution in limit of vanishing time step. It preserves magnetization magnitude and main energy balance properties LLG equation independently then study superparamagnetic state a small spheroidal particle, results are compared with theory.
Energy-efficient switching of magnetization is a central problem in nonvolatile magnetic storage and neuromorphic computing. In the past two decades, several efficient methods were demonstrated including spin torque, magneto-electric, microwave-assisted mechanisms. Here we experimentally show that low-dimensional chaos induced by alternating torque can strongly increase rate thermally-activated nanoscale ferromagnet. This mechanism exhibits well-pronounced threshold character amplitude its...
Methods of nonlinear-dynamical-system theory are applied to the study magnetization dynamics under action microwave magnetic fields. In case a system with uniaxial anisotropy subject circularly-polarized field, conditions derived which reversal field is substantially reduced by application field. The dependence switching on microwave-field-pulse duration discussed and analytical expressions for minimum pulse leading switching.
The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain rate of ICD, resulting yield Ne_{2}^{+} ions was recorded as a function delay between pump and UV probe pulses. extracted lifetimes long-lived states, 390(-130/+450)...
We present a comprehensive experimental and numerical study of magnetization dynamics in thin metallic film triggered by single-cycle terahertz pulses $\ensuremath{\sim}20\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ electric field amplitude $\ensuremath{\sim}1\text{ }\mathrm{ps}$ duration. The is probed using the femtosecond magneto-optical Kerr effect, it reproduced numerically macrospin simulations. can be decomposed three distinct processes: coherent precession around magnetic field, an...
A rigorous analysis of the precessional switching dynamics in uniformly magnetized particles and films is presented. Magnetization are described by Landau–Lifshitz equation realized applying a field pulse orthogonal to easy axis particle or film. The process based on explicit knowledge two integrals motion for magnetization leads closed form analytical expressions terms Jacobi elliptic functions. It shown that can occur only beyond critical threshold. solutions used predict trajectory time...
The injection-locking mechanism of a spin-transfer nano-oscillator is studied for system which traversed by spin-polarized electric current with both dc and ac components. uniform mode theory used to predict the control parameters synchronization between magnetization self-oscillation external microwave current. It found that micromagnetic simulations at zero temperature are in very good agreement theory, showing dynamics practically space. Then, effect on synchronized regimes analyzed....
We study magnetization dynamics in spin-transfer devices subject to DC and microwave injected currents. When the frequency of current is sufficiently close self-oscillation device, phase-locking occurs. This phenomenon theoretically studied by using Landau-Lifshitz equation with Slonczewski spin-torque term. By exploiting separation time scales averaging technique, we derive equations which are applicable for arbitrary large motion. The stability diagram (detuning, ac current)-plane...
Ne clusters (∼5000 atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply can decay nonradiatively via energy exchange between least two neighboring atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites probed. We found that relaxation cluster surface atoms proceeds a sequence interatomic or intermolecular Coulombic (ICD) processes while ICD bulk is additionally affected surrounding...
A new technique of magnetic imaging on a spin stand has been developed. In this technique, raw image acquisition is performed by scanning target area disk conventional magneto-resistive (MR) read head in two orthogonal (along- and cross-track) directions. Due to the nonlocalized nature MR reading cross-track direction, reconstruction needed order retrieve actual distribution magnetization. It demonstrated that can be using response function characterization specially designed deconvolution...