Invited Speaker CURRENT-INDUCED DOMAIN WALL DYNAMICS

When combining transport with magnetic materials on the nanoscale, a range of exciting and novel phenomena emerge. Due to the interaction of the current with the magnetization, the spin transfer torque effect leads to current-induced domain wall motion (CIDM) [1-3], which we study in detail. In CIDM, electrons transfer angular momentum and thereby push a domain wall [1-3]. We have comprehensively investigated this effect and observed that this interaction is strongly dependent on the temperature [3] and the wall spin structure [2]. So far, primarily current pulses have been employed to investigate domain wall displacements and strongly stochastic behaviour has been observed. More reproducible behaviour is found if AC currents are used to excite domain wall oscillations, which are inherently reproducible. To generate a domain wall oscillator a restoring force is necessary, which can be provided by a constriction that generates an attractive potential well for a domain wall, which then acts as a quasiparticle [4]. The depth of the potential well, was found to increase with decreasing constriction width, and the well width was found to extend far beyond the physical size of the constriction [4]. To fully characterize the pinning potential, the curvature has to be determined in addition to the width and the depth. To study the curvature, the resonance frequency of the domain wall has to be ascertained and to this end, we inject AC currents with variable frequency into the structure shown in Fig. 1 (a) [5]. We the