Time: Tuesday, October 23rd, 17:00
Speaker: Carl DAVIES, Nijmegen
Ever-increasing demand for faster and more energy-efficient information processing and storage has fuelled intense fundamental studies on the magnetization dynamics displayed by ferroics. Here, we experimentally and numerically explore how magnetization dynamics within the dielectric bismuth-substituted yttrium iron garnet (Bi:YIG) can be controlled using the thermal load associated with a laser pulse. In particular, we focus on how a laser-induced diminishment of the growth-induced crystalline anisotropy can affect magnetization reversal and domain-wall motion, thus revealing a new degree of freedom for the optical control of magnetism.
In the first set of experiments and calculations, we show that non-linear precessional magnetization dynamics can be triggered in Bi:YIG via a laser-induced modification of the effective magnetic field. Indeed, the amplitude of the resulting precession can be large enough to allow for magnetic recording at sub-nanosecond timescales, within just one-half of a precessional period. Surprisingly, we observe that the magnetic damping becomes anomalously large during the switching process, rendering the switching route robust.
In the second set of experiments, we explore how the velocity of moving domain walls (DWs) can be affected by a laser pulse. Using the technique of double photography, we show that the impact of light on the DW velocity is a function of the optical intensity and the velocity itself. The results are explained in terms of interplay between photo-induced localization of Bloch lines, due to local intensity-dependent change of the magnetic anisotropy, and the velocity-dependent Magnus force which inhibits localization of Bloch-lines.