Search results for "DOM"
showing 10 items of 12668 documents
Enhancing domain wall velocity through interface intermixing in W-CoFeB-MgO films with perpendicular anisotropy
2019
We study the influence of He+ irradiation induced interface intermixing on magnetic domain wall (DW) dynamics in W-CoFeB (0.6 nm)-MgO ultrathin films, which exhibit high perpendicular magnetic anisotropy and large Dzyaloshinskii-Moriya interaction (DMI) values. Whereas the pristine films exhibit strong DW pinning, we observe a large increase in the DW velocity in the creep regime upon He+ irradiation, which is attributed to the reduction of pinning centers induced by interface intermixing. Asymmetric in-plane field-driven domain expansion experiments show that the DMI value is slightly reduced upon irradiation, and a direct relationship between DMI and interface anisotropy is demonstrated. …
State-space formulation of scalar Preisach hysteresis model for rapid computation in time domain
2015
A state-space formulation of classical scalar Preisach model (CSPM) of hysteresis is proposed. The introduced state dynamics and memory interface allow to use the state equation, which is rapid in calculation, instead of the original Preisach equation. The main benefit of the proposed modeling approach is the reduced computational effort which requires only a single integration over the instantaneous line segment in the Preisach plane. Numerical evaluations of the computation time and model accuracy are provided in comparison to the CSPM which is taken as a reference model.
Strain detection in non-magnetic steel by Kerr-microscopy of magnetic tracer layers
2018
Abstract For many applications of steel, e.g. for the evaluation of the fatigue state of components or structures, the characterization of the microscopic strain distribution in the material is important. We present a proof-of-principle for the visualization of such strain distributions by Kerr-microscopy of ferromagnetic tracer layers on nonmagnetic steel sheets. The influence of indentation induced strain on the magnetic domain pattern of 20 nm Galfenol and Permalloy tracer layers on austenitic AISI 904L steel sheets was investigated. The obtained Kerr-microscopy images show a characteristic domain pattern in the strained regions of the steel sheets, which is consistent with a dominant ma…
Electromechanical properties of Na 0.5 Bi 0.5 TiO 3 -SrTiO 3 -PbTiO 3 solid solutions
2018
Abstract Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Ray…
Structural phase transition in [(C2H5)4N][(CH3)4N]ZnCl4
2019
The hybrid crystal [(C2H5)4N][(CH3)4N]ZnCl4 was studied using several experimental methods. DSC studies revealed the first order phase transition to the high temperature phase at about 496 K. This phase transition was confirmed in dielectric studies. Optical observation revealed the domain structure appearance characteristic for that of the phase transition between tetragonal and orthorhombic phases. This phase transition shows a lowering of symmetry as in the case of bromide analogs. Additionally, the optical studies showed the appearance of a number of cracks in the sample and in some cases, the samples became milky after cooling from the high temperature to the room temperature phase.
Unusual domain-wall motion in ferromagnetic semiconductor films with tetragonal anisotropy
2009
International audience; Magnetic field-driven domain-wall propagation in the flow regime is investigated in (Ga, Mn) As ferromagnetic semiconductor layers. Square-shape magnetic domains with an unexpected orientation of their edges, at pi/8 with respect to the anisotropy axes, are found. This is shown to arise from the effect of tetragonal magnetic anisotropy on domain-wall dynamics. Using a one-dimensional model for domain-wall motion and modeling domain growth by contour dynamics the shape and orientation of domains and their field range for existence are well reproduced. These results point to the key role of the vectorial nature of the order parameter in the dynamics of ferromagnetic do…
Switching by Domain-Wall Automotion in Asymmetric Ferromagnetic Rings
2017
A ring-shaped magnetic logic device offers two vortex states (clockwise and counterclockwise) to encode bits, with relative stability against external magnetic fields. The dynamics of magnetization switching in such structures, though, still need unraveling. The authors present direct experimental visualization of reproducible, robust switching in magnetic rings via domain-wall automotion, which does not require an applied field. Simulations reveal that annihilation of domain walls through automotion always occurs, with the detailed topology of the walls only influencing the dynamics locally, in line with the experimental results.
The Role of Right Interpretation of Space Charge Distribution for Optimized Design of HVDC Cables
2019
In the field of high-voltage transmission systems, different degradation phenomena affect the reliability of the employed components. In particular, under dc stress, the space charge accumulation phenomenon is believed to be the most responsible of the dielectrics lifetime reduction. To measure the accumulated space charges in flat specimens, the pulsed electro-acoustic (PEA) method is one of the most used techniques. The working principle of the PEA cell is based on the acoustic waves propagation and detection. As is well known, the acoustic waves propagating in different means are partially transmitted and partially reflected. Therefore, the piezoelectric sensor of the PEA cell is subject…
Synchronous precessional motion of multiple domain in a ferromagnetic nanowire by perpendicular field pulses
2014
Magnetic storage and logic devices based on magnetic domain wall motion rely on the precise and synchronous displacement of multiple domain walls. The conventional approach using magnetic fields does not allow for the synchronous motion of multiple domains. As an alternative method, synchronous current-induced domain wall motion was studied, but the required high-current densities prevent widespread use in devices. Here we demonstrate a radically different approach: we use out-of-plane magnetic field pulses to move in-plane domains, thus combining field-induced magnetization dynamics with the ability to move neighbouring domain walls in the same direction. Micromagnetic simulations suggest …
Current induced chiral domain wall motion in CuIr/CoFeB/MgO thin films with strong higher order spin–orbit torques
2020
We investigate the Dzyaloshinskii–Moriya interaction (DMI) and spin–orbit torque effects in CuIr/CoFeB/MgO heterostructures. To this end, harmonic Hall measurements and current induced domain wall motion experiments are performed. The motion of domain walls at zero applied field due to current demonstrates the presence of DMI in this system. We determine the strength of the DMI to be D = + 5 ± 3 μ J / m 2 and deduce right-handed chirality in domain walls showing a partial Neel type spin structure. To ascertain the torques, we perform a second harmonic measurement to quantify the damping- and field-like current induced effective fields as a function of the magnetization direction. From the a…