Browsing by Author "Van De Wiele, Ben"

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Electric-field-driven dynamics of magnetic domain walls in magnetic nanowires patterned on ferroelectric domains
(2016-03-16) Van De Wiele, Ben; Leliaert, Jonathan; Franke, Kévin J A; Van Dijken, Sebastiaan
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Strong coupling of magnetic domain walls onto straight ferroelastic boundaries of a ferroelectric layer enables full and reversible electric-field control of magnetic domain wall motion. In this paper, the dynamics of this new driving mechanism is analyzed using micromagnetic simulations. We show that transverse domain walls with a near-180° spin structure are stabilized in magnetic nanowires and that electric fields can move these walls with high velocities. Above a critical velocity, which depends on material parameters, nanowire geometry and the direction of domain wall motion, the magnetic domain walls depin abruptly from the ferroelastic boundaries. Depinning evolves either smoothly or via the emission and annihilation of a vortex or antivortex core (Walker breakdown). In both cases, the magnetic domain wall slows down after depinning in an oscillatory fashion and eventually comes to a halt. The simulations provide design rules for hybrid ferromagnetic-ferroelectric domain-wall-based devices and indicatethat material disorder and structural imperfections only influence Walker-breakdown-like depinning at high domain wall velocities.
Reconfigurable magnetic logic based on the energetics of pinned domain walls
(2016-01-18) López González, Diego; Casiraghi, Arianna; Van De Wiele, Ben; Van Dijken, Sebastiaan
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A magnetic logic concept based on magnetic switching in three stripe domains separated by pinned magnetic domain walls is proposed. The relation between the inputs and the output of the logic operator is determined by the energetics of the domain walls, which can be switched between two distinctive states by an external magnetic field. Together with magnetic read-out along two orthogonal directions, non-volatile AND, OR, NAND, and NOR gates can be created. The logic concept is experimentally demonstrated using CoFeB films on BaTiO3 substrates, and micromagnetic simulations are used to analyze the energetics of the system.
Tunable short-wavelength spin wave excitation from pinned magnetic domain walls
(2016-02-17) Van De Wiele, Ben; Hämälaïnen, Sampo J.; Baláz, Pavel; Montoncello, Federico; Van Dijken, Sebastiaan
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors.