Greatly enhanced magneto-optic detection of single nanomagnets using focused magnetoelastic excitation

Abstract

Magnetization dynamics of nanomagnets directly determine the performance of magnetic storage and memory devices. Here, we report a 10-times enhancement of magnetization dynamics excitation of single nanomagnets using focused surface acoustic waves (SAWs), compared to conventional optical excitation. SAWs are generated via ultrafast optical excitation of an arc-shaped phononic grating and focused onto a single nanomagnet located at the focal spot of the grating. Thanks to the robust resonance excitation, we observe the strain-controlled ultrafast magnetization dynamics in a sub-100 nm single nanomagnet. This improved excitation efficiency was applied to exciting SAWs in four sets of gratings with different pitches using a single laser spot. This enabled selective excitation of any one of four identical nanomagnets at different frequencies simply by tuning an external magnetic field. This all-optical technique provides a method of addressing individual magnetic nano-oscillators and studying their intrinsic magnetization dynamics.