Search results for "Perpendicular"
showing 10 items of 168 documents
Spin Logical and Memory Device Based on the Nonvolatile Ferroelectric Control of the Perpendicular Magnetic Anisotropy in PbZr 0.2 Ti 0.8 O 3 /Co/Pt …
2020
Phase separation of binary mixtures in thin films: Effects of an initial concentration gradient across the film.
2012
We study the kinetics of phase separation of a binary (A,B) mixture confined in a thin film of thickness $D$ by numerical simulations of the corresponding Cahn-Hilliard-Cook (CHC) model. The initial state consisted of 50$%$ A:50$%$ B with a concentration gradient across the film, i.e., the average order parameter profile is ${\ensuremath{\Psi}}_{\mathrm{av}}(z,t=0)=(2z/D\ensuremath{-}1){\ensuremath{\Psi}}_{g},\phantom{\rule{0.28em}{0ex}}0\ensuremath{\leqslant}z\ensuremath{\leqslant}D$, for various choices of ${\ensuremath{\Psi}}_{g}$ and $D$. The equilibrium state (for time $t\ensuremath{\rightarrow}\ensuremath{\infty}$) consists of coexisting A-rich and B-rich domains separated by interfac…
Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized W/CoFeB/MgO Films
2020
Controlling magnetism by electric fields offers a highly attractive perspective for designing future generations of energy-efficient information technologies. Here, we demonstrate that the magnitude of current-induced spin-orbit torques in thin perpendicularly magnetized CoFeB films can be tuned and even increased by electric-field generated piezoelectric strain. Using theoretical calculations, we uncover that the subtle interplay of spin-orbit coupling, crystal symmetry, and orbital polarization is at the core of the observed strain dependence of spin-orbit torques. Our results open a path to integrating two energy efficient spin manipulation approaches, the electric-field-induced strain a…
Curvature as a Guiding Field for Patterns in Thin Block Copolymer Films
2018
Experimental data on thin films of cylinder-forming block copolymers (BC)—free-standing BCmembranes as well as supported BC films—strongly suggest that the local orientation of the BC patternsis coupled to the geometry in which the patterns are embedded. We analyze this phenomenon using generalsymmetry considerations and numerical self-consistent field studies of curved BC films in cylindricalgeometry. The stability of the films against curvature-induced dewetting is also analyzed. In goodagreement with experiments, we find that the BC cylinders tend to align along the direction of curvature athigh curvatures. At low curvatures, we identify a transition from perpendicular to parallel alignm…
Faceting and structural anisotropy of nanopatterned CdO(110) layers
2005
CdO(110) layers with a self-organized surface structure have been grown on (10math0) sapphire (m plane) substrates by metal-organic vapor phase epitaxy. The epitaxial relationships between layer and substrate have been determined and a crystallographic model that accounts for the CdO in-plane orientation, which results in a reduced lattice mismatch when the CdO[001] direction is perpendicular to the sapphire c axis, has been proposed. Although the measured lattice parameters indicate that the layers are almost fully relaxed, an anisotropic mosaicity is detected with symmetrical rocking curves attaining minimum values when measured along the CdO[math10] direction. The layer morphology consis…
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.
Current-Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures.
2018
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Magnetic skyrmions promise breakthroughs in future memory and computing devices due to their inherent stability and small size. Their creation and current driven motion have been recently observed at room temperature, but the key mechanisms of their formation are not yet well-understood. Here it is shown that in heavy metal/ferromagnet heterostructures, pulsed currents can drive morphological transitions between labyrinth-like, stripe-like, and skyrmionic states. Using high-resolution X-ray microscopy, the spin texture evolution with temperature and magnetic field is imaged and it is demonstrated that with transient Joule heating, topologica…
The Effect of Damage and Geometrical Variability on the Tensile Strength Distribution of Flax Fibers
2010
Natural fibers of plant origin are finding non-traditional applications as reinforcement of composite materials. The mechanical properties of fibers exhibit considerable scatter, being affected by the natural variability in plant as well as the damage accumulated during processing. For bast fibers, the primary damage mode is kink bands – zones of misaligned cellulose microfibrils extending across the fiber and oriented roughly perpendicularly to its axis. Another feature typical for natural fibers and contributing to the scatter of fiber strength is the variability of diameter along a fiber length and among the fibers. An analytical expression for the distribution of the longitudinal tensil…
Grafted polymer layers under shear: A Monte Carlo simulation
1993
Endgrafted polymers at surfaces exposed to a shear flow are modeled by a nonequilibrium Monte Carlo method where the jump rate of effective monomers to neighboring lattice sites against the flow direction is smaller than in the flow direction, assuming that this difference in jump rates is proportional to the local velocity of the flowing fluid. In the dilute case of isolated chains, the velocity profile is assumed linearly increasing with the distance from the surface, while for the case of polymer brushes the screening of the velocity field is calculated using a parabolic density profile for the brush whose height is determined self‐consistently. Linear dimensions of isolated chains are o…
Switching direction of laterally ordered monolayers induced by transfer instability
2007
Langmuir-Blodgett monolayers may show nanoscopic periodic patterns parallel and/or perpendicular to the transfer direction. The experimental findings are interpreted by a nonequilibrium model based on the stability of surfactant concentration and film thickness coupled fluctuations near the meniscus of a surfactant-covered receding thin film. In the high and low transfer speed limits, periodic fluctuations of the fluid subphase thickness, respectively perpendicular and parallel to the transfer, are selected. A qualitative phase diagram shows how transfer speed and film density manage the pattern shape.