Search results for "WALL"
showing 10 items of 970 documents
Strain-controlled domain wall injection into nanowires for sensor applications
2021
We investigate experimentally the effects of externally applied strain on the injection of 180$^\circ$ domain walls (DW) from a nucleation pad into magnetic nanowires, as typically used for DW-based sensors. In our study the strain, generated by substrate bending, induces in the material a uniaxial anisotropy due to magnetoelastic coupling. To compare the strain effects, $Co_{40}Fe_{40}B_{20}$, $Ni$ and $Ni_{82}Fe_{18}$ samples with in-plane magnetization and different magnetoelastic coupling are deposited. In these samples, we measure the magnetic field required for the injection of a DW, by imaging differential contrast in a magneto-optical Kerr microscope. We find that strain increases t…
Facilitating domain wall injection in magnetic nanowires by electrical means
2020
We investigate how to facilitate the injection of domain walls in chiral ferromagnetic nanowires by electrical means. We calculate the critical current density above which domain walls are injected into the nanowire depending on the material parameters and the source of interaction including spin-transfer torques as well as spin-orbit torques. We demonstrate that the Dzyaloshinskii-Moriya interaction can significantly reduce the required critical current to inject the types of domain walls favored by the Dzyaloshinskii-Moriya interaction. We find that in chiral magnets it is only possible to shed a single domain wall by means of spin-orbit torques, as they modify the ground state orientatio…
Nonresonant hole burning spectroscopy of the relaxor ferroelectric PLZT
2002
Abstract The polydispersive dielectric response of a lanthanum-modified lead zirconate titanate relaxor ferroelectric was studied using nonresonant hole burning (NHB) spectroscopy. The dynamic heterogeneity of this material was evidenced by the fact that it was possible to burn frequency-dependent spectral holes. The maximum position of the spectral holes depended on the square root of the pump frequency Ω . The refilling of the spectral holes was monitored subsequent to excitation using various pump frequencies. The refilling data could be collapsed onto a master curve by re-scaling them, again, using Ω −0.5 as scaling factor. The refilling time was found to be much longer than the time sc…
Ferroelectricity and structure of BaTiO grown on YBa Cu O thin films
2000
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O \(_{7 - \delta }\) as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O \(_{7 - \delta }\) and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction. The ferroelectric behaviour of the BaTiO3 films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm and a remanent polarisation of 1.25 μC/cm2. At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indica…
Carbon nanotubes under electron irradiation: Stability of the tubes and their action as pipes for atom transport
2005
The production and migration of carbon interstitials in carbon nanotubes under electron irradiation is studied experimentally and theoretically. It is shown that the threshold for displacing carbon atoms and the defect production rate strongly depend on the diameter of the nanotubes. Multiwalled nanotubes shrink by a loss of atoms and by diffusion of interstitials through the inner hollow in the axial direction. Thus, experimental evidence is given that nanotubes can act as nanoscale pipes for the transport of atoms.
Graphene, Fullerenes, Carbon Nanotubes: Electronic Subsystem
2017
This chapter introduces the reader to the analysis of the structural and electronic system properties of various carbon allotropes (CNT, graphene) and several molecular derivatives. The genesis of the electronic system formation is investigated in detail. Non-regular defected nanocarbon systems are considered for possible applications in different fields, including energy storage; chemical, biochemical and electrochemical sensing; water purification; and catalysis.
Comparison between a Uniaxial Compaction Tester and a Shear Tester for the Characterization of Powder Flowability
2014
The complete characterization of powder flow properties with shear cells is a long and time-consuming process that requires specially trained operators or costly automated instruments. For these reasons, in industrial practice, the use of simpler and less extensive measurement by uniaxial compaction testers is often preferred. However, previous studies in the literature indicate that the results of the two techniques are not directly comparable due to the different stress state conditions achieved in the two testers.In this study, an experimental campaign to measure the flow function of five different powders with a ring shear tester (RST) and a uniaxial compaction tester (UCT) was performe…
Coded excitation speeds up the detection of the fundamental flexural guided wave in coated tubes
2016
The fundamental flexural guided wave (FFGW) permits ultrasonic assessment of the wall thickness of solid waveguides, such as tubes or, e.g., long cortical bones. Recently, an optical non-contact method was proposed for ultrasound excitation and detection with the aim of facilitating the FFGW reception by suppressing the interfering modes from the soft coating. This technique suffers from low SNR and requires iterative physical scanning across the source-receiver distance for 2D-FFT analysis. This means that SNR improvement achieved by temporal averaging becomes time-consuming (several minutes) which reduces the applicability of the technique, especially in time-critical applications such as…
Current-induced fingering instability in magnetic domain walls
2015
The shape instability of magnetic domain walls under current is investigated in a ferromagnetic (Ga,Mn)(As,P) film with perpendicular anisotropy. Domain wall motion is driven by the spin transfer torque mechanism. A current density gradient is found either to stabilize domains with walls perpendicular to current lines or to produce finger-like patterns, depending on the domain wall motion direction. The instability mechanism is shown to result from the non-adiabatic contribution of the spin transfer torque mechanism.
Quantum Rescaling, Domain Metastability, and Hybrid Domain‐Walls in 2D CrI3 Magnets
2020
Higher-order exchange interactions and quantum effects are widely known to play an important role in describing the properties of low-dimensional magnetic compounds. Here, the recently discovered 2D van der Waals (vdW) CrI3 is identified as a quantum non-Heisenberg material with properties far beyond an Ising magnet as initially assumed. It is found that biquadratic exchange interactions are essential to quantitatively describe the magnetism of CrI3 but quantum rescaling corrections are required to reproduce its thermal properties. The quantum nature of the heat bath represented by discrete electron-spin and phonon-spin scattering processes induces the formation of spin fluctuations in the …