Browsing by Author "Van de Wiele, Ben"
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- Creep turns linear in narrow ferromagnetic nanostrips
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-02-04) Leliaert, Jonathan; Van de Wiele, Ben; Vansteenkiste, Arne; Laurson, Lasse; Durin, Gianfranco; Dupre, Luc; Van Waeyenberge, BartelThe motion of domain walls in magnetic materials is a typical example of a creep process, usually characterised by a stretched exponential velocity-force relation. By performing large-scale micromagnetic simulations, and analyzing an extended 1D model which takes the effects of finite temperatures and material defects into account, we show that this creep scaling law breaks down in sufficiently narrow ferromagnetic strips. Our analysis of current-driven transverse domain wall motion in disordered Permalloy nanostrips reveals instead a creep regime with a linear dependence of the domain wall velocity on the applied field or current density. This originates from the essentially point-like nature of domain walls moving in narrow, line-like disordered nanostrips. An analogous linear relation is found also by analyzing existing experimental data on field-driven domain wall motion in perpendicularly magnetised media. - Electric field driven magnetic domain wall motion in ferromagnetic-ferroelectric heterostructures
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014) Van de Wiele, Ben; Laurson, Lasse; Franke, Kevin J. A.; van Dijken, SebastiaanWe investigate magnetic domain wall (MDW) dynamics induced by applied electric fields in ferromagnetic-ferroelectric thin-film heterostructures. In contrast to conventional driving mechanisms where MDW motion is induced directly by magnetic fields or electric currents, MDW motion arises here as a result of strong pinning of MDWs onto ferroelectric domain walls (FDWs) via local strain coupling. By performing extensive micromagnetic simulations, we find several dynamical regimes, including instabilities such as spin wave emission and complex transformations of the MDW structure. In all cases, the time-averaged MDW velocity equals that of the FDW, indicating the absence of Walker breakdown. - Electric-field-driven domain wall dynamics in perpendicularly magnetized multilayers
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017-03) Gonzalez, Diego Lopez; Shirahata, Yasuhiro; Van de Wiele, Ben; Franke, Kevin J. A.; Casiraghi, Arianna; Taniyama, Tomoyasu; van Dijken, SebastiaanWe report on reversible electric-field-driven magnetic domain wall motion in a Cu/Ni multilayer on a ferroelectric BaTiO3 substrate. In our heterostructure, strain-coupling to ferroelastic domains with in-plane and perpendicular polarization in the BaTiO3 substrate causes the formation of domains with perpendicular and in-plane magnetic anisotropy, respectively, in the Cu/Ni multilayer. Walls that separate magnetic domains are elastically pinned onto ferroelectric domain walls. Using magneto-optical Kerr effect microscopy, we demonstrate that out-of-plane electric field pulses across the BaTiO3 substrate move the magnetic and ferroelectric domain walls in unison. Our experiments indicate an exponential increase of domainwall velocity with electric field strength and opposite domain wall motion for positive and negative field pulses. The application of a magnetic field does not affect the velocity of magnetic domain walls, but independently tailors their internal spin structure, causing a change in domain wall dynamics at high velocities. (C) 2017 Author(s). - Reconfigurable magnetic logic based on the energetics of pinned domain walls
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016) López González, Diego; Casiraghi, Arianna; Van de Wiele, Ben; van Dijken, SebastiaanA 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 simulationsare used to analyze the energetics of the system. - Reversible Electric-Field-Driven Magnetic Domain-Wall Motion
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2015) Franke, Kevin J. A.; Van de Wiele, Ben; Shirahata, Yasuhiro; Hämäläinen, Sampo J.; Taniyama, Tomoyasu; van Dijken, SebastiaanControl of magnetic domain-wall motion by electric fields has recently attracted scientific attention because of its potential for magnetic logic and memory devices. Here, we report on a new driving mechanism that allows for magnetic domain-wall motion in an applied electric field without the concurrent use of a magnetic field or spin-polarized electric current. The mechanism is based on elastic coupling between magnetic and ferroelectric domain walls in multiferroic heterostructures. Pure electric-field-driven magnetic domain-wall motion is demonstrated for epitaxial Fe films on BaTiO3 with in-plane and out-of-plane polarized domains. In this system, magnetic domain-wall motion is fully reversible and the velocity of the walls varies exponentially as a function of out-of-plane electric-field strength.