Intrinsic Nature of Stochastic Domain Wall Pinning Phenomena in Magnetic Nanowire Devices.
Ontology highlight
ABSTRACT:
SUBMITTER: Hayward TJ
PROVIDER: S-EPMC4548438 | biostudies-other | 2015
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Nanofabrication has allowed the development of new concepts such as magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls on magnetic nanostripes. One of the issues that has to be solved before devices can meet the market demands is the stochastic behaviour of the domain wall movement in magnetic nanostripes. Here we show that the stochastic nature of the domain wall motion in permalloy nanostripes can be suppressed at very low fields (0.6-2.7 Oe). We also find different field regimes for this stochastic motion that match well with the domain wall propagation modes. The highest pinning probability is found around the precessional mode and, interestingly, it does not depend on the external field in this regime. These results constitute an experimental evidence of the intrinsic nature of the stochastic pinning of domain walls in soft magnetic nanostripes.
| S-EPMC3482628 | biostudies-other
Project description:Understanding dynamically-induced stochastic switching effects in soft ferromagnetic nanowires is a critical challenge for realising spintronic devices with deterministic switching behaviour. Here, we present a micromagnetic simulation protocol for qualitatively predicting dynamic stochastic domain wall (DW) pinning/depinning at artificial defect sites in Ni80Fe20 nanowires, and demonstrate its abilities by correlating its predictions with the results of focused magneto-optic Kerr effect measurements. We analyse DW pinning configurations in both thin nanowires (t?=?10?nm) and thick nanowires (t?=?40?nm) with both single (asymmetric) and double (symmetric) notches, showing how our approach provides understanding of the complex DW-defect interactions at the heart of stochastic pinning behaviours. Key results explained by our model include the total suppression of stochastic pinning at single notches in thick nanowires and the intrinsic stochasticity of pinning at double notches, despite their apparent insensitivity to DW chirality.
| S-EPMC5736692 | biostudies-other
Project description:The three dimensional nature of cylindrical magnetic nanowires has opened a new way to control the domain configuration as well as the magnetization reversal process. The pinning effect of the periodic diameter modulations on the domain wall propagation in FeCoCu individual nanowires is determined by Magnetic Force Microscopy, MFM. A main bistable magnetic configuration is firstly concluded from MFM images characterized by the spin reversal between two nearly single domain states with opposite axial magnetization. Complementary micromagnetic simulations confirm a vortex mediated magnetization reversal process. A non-standard variable field MFM imaging procedure allows us to observe metastable magnetic states where the propagating domain wall is pinned at certain positions with enlarged diameter. Moreover, it is demonstrated that it is possible to control the position of the pinned domain walls by an external magnetic field.
| S-EPMC4942567 | biostudies-literature
Project description:Ferroelectric materials possess a spontaneous polarization that is switchable by an electric field. Robust retention of switched polarization is critical for non-volatile nanoelectronic devices based on ferroelectrics, however, these materials often suffer from polarization relaxation, typically within days to a few weeks. Here we exploit designer-defect-engineered epitaxial BiFeO3 films to demonstrate polarization retention with virtually no degradation in switched nanoscale domains for periods longer than 1 year. This represents a more than 2000% improvement over the best values hitherto reported. Scanning probe microscopy-based dynamic switching measurements reveal a significantly increased activation field for domain wall movement. Atomic resolution scanning transmission electron microscopy indicates that nanoscale defect pockets pervade the entire film thickness. These defects act as highly efficient domain wall pinning centres, resulting in anomalous retention. Our findings demonstrate that defects can be exploited in a positive manner to solve reliability issues in ferroelectric films used in functional devices.
| S-EPMC6969134 | biostudies-literature
Project description:The emergence of atomically thin van der Waals magnets provides a new platform for the studies of two-dimensional magnetism and its applications. However, the widely used measurement methods in recent studies cannot provide quantitative information of the magnetization nor achieve nanoscale spatial resolution. These capabilities are essential to explore the rich properties of magnetic domains and spin textures. Here, we employ cryogenic scanning magnetometry using a single-electron spin of a nitrogen-vacancy center in a diamond probe to unambiguously prove the existence of magnetic domains and study their dynamics in atomically thin CrBr3. By controlling the magnetic domain evolution as a function of magnetic field, we find that the pinning effect is a dominant coercivity mechanism and determine the magnetization of a CrBr3 bilayer to be about 26 Bohr magnetons per square nanometer. The high spatial resolution of this technique enables imaging of magnetic domains and allows to locate the sites of defects that pin the domain walls and nucleate the reverse domains. Our work highlights scanning nitrogen-vacancy center magnetometry as a quantitative probe to explore nanoscale features in two-dimensional magnets.
| S-EPMC8012586 | biostudies-literature
Project description:"Domain wall traps" have been engineered and well-exploited in nanostrips by creating a geometrical trapping site, e.g. a single notch along a stripe, compared to diameter-modulated (DM) cylindrical magnetic nanowires (NWs) where multi-segmented DM-NWs have been generally studied. Here, we report our systematic study on the magnetization behavior, domain wall structure and its nucleation/propagation in tri-segmented diameter-modulated Ni nanowires, a simple system to investigate the magnetization reversal as function of segment geometry and lay-out order. We find out that the magnetization behavior of single Ni DM-NWs exhibits the significance of positional ordering of thick and thin segments, distinguished by two distinct geometries including: dumbbell-type (type I) and rolling pin-type (type II). Based on experimental and theoretical simulations, it was evidenced that the wide-narrow junctions create trap sites for domain walls where the narrow segment restricts their motion. This type of geometrically engineered nanowires exhibit potential efficiency for future novel spintronic devices in particular when assembled in arrays of DM-NWs as a practical three-dimensional memory device.
| S-EPMC6588627 | biostudies-literature
Project description:Some of the best-performing high-temperature magnets are Sm-Co-based alloys with a microstructure that comprises an [Formula: see text] matrix and magnetically hard [Formula: see text] cell walls. This generates a dense domain-wall-pinning network that endows the material with remarkable magnetic hardness. A precise understanding of the coupling between magnetism and microstructure is essential for enhancing the performance of Sm-Co magnets, but experiments and theory have not yet converged to a unified model. Here, transmission electron microscopy, atom probe tomography, and nanometer-resolution off-axis electron holography have been combined with micromagnetic simulations to reveal that the magnetization state in Sm-Co magnets results from curling instabilities and domain-wall pinning effects at the intersections of phases with different magnetic hardness. Additionally, this study has found that topologically non-trivial magnetic domains separated by a complex network of domain walls play a key role in the magnetic state by acting as nucleation sites for magnetization reversal. These findings reveal previously hidden aspects of magnetism in Sm-Co magnets and, by identifying weak points in the microstructure, provide guidelines for improving these high-performance magnetic materials.
| S-EPMC7713442 | biostudies-literature
Project description:Magnetic domain wall motion could be the key to the next generation of data storage devices, shift registers without mechanically moving parts. Various concepts of such so-called 'racetrack memories' have been developed, but they are usually plagued by the need for high current densities or complex geometrical requirements. We introduce a new device concept, based on the interfacial Dzyaloshinskii-Moriya interaction (DMI), of which the importance in magnetic thin films was recently discovered. In this device the domain walls are moved solely by magnetic fields. Unidirectionality is created utilizing the recent observation that the strength with which a domain wall is pinned at an anisotropy barrier depends on the direction of the in-plane field due to the chiral nature of DMI. We demonstrate proof-of-principle experiments to verify that unidirectional domain-wall motion is achieved and investigate several material stacks for this novel device including a detailed analysis of device performance for consecutive pinning and depinning processes.
| S-EPMC5429776 | biostudies-literature
Project description:Introducing artificial pinning centers is a well established strategy to trap quantum vortices and increase the maximal magnetic field and applied electric current that a superconductor can sustain without dissipation. In case of spatially periodic pinning, a clear enhancement of the superconducting critical current arises when commensurability between the vortex configurations and the pinning landscape occurs. With recent achievements in (ultrafast) optics and nanoengineered plasmonics it has become possible to exploit the interaction of light with superconductivity, and create not only spatially periodic imprints on the superconducting condensate, but also temporally periodic ones. Here we show that in the latter case, temporal matching phenomena develop, caused by stroboscopic commensurability between the characteristic frequency of the vortex motion under applied current and the frequency of the dynamic pinning. The matching resonances persist in a broad parameter space, including magnetic field, driving current, or material purity, giving rise to unusual features such as externally variable resistance/impedance and Shapiro steps in current-voltage characteristics. All features are tunable by the frequency of the dynamic pinning landscape. These findings open further exploration avenues for using flashing, spatially engineered, and/or mobile excitations on superconductors, permitting us to achieve advanced functionalities.
| S-EPMC4589687 | biostudies-literature
Project description:A higher saturation magnetization obtained by an increased iron content is essential for yielding larger energy products in rare-earth Sm2Co17-type pinning-controlled permanent magnets. These are of importance for high-temperature industrial applications due to their intrinsic corrosion resistance and temperature stability. Here we present model magnets with an increased iron content based on a unique nanostructure and -chemical modification route using Fe, Cu, and Zr as dopants. The iron content controls the formation of a diamond-shaped cellular structure that dominates the density and strength of the domain wall pinning sites and thus the coercivity. Using ultra-high-resolution experimental and theoretical methods, we revealed the atomic structure of the single phases present and established a direct correlation to the macroscopic magnetic properties. With further development, this knowledge can be applied to produce samarium cobalt permanent magnets with improved magnetic performance.Understanding the factors that determine the properties of permanent magnets, which play a central role in many industrial applications, can help in improving their performance. Here, the authors study how changes in the iron content affect the microstructure of samarium cobalt magnets.
| S-EPMC5496909 | biostudies-literature