Opto-magnonic crystals: optical manipulation of spin waves

It is well-recognized in condensed matter physics that structural and magnetic properties are intimately connected; thus controlling structure has been a successful route to controlling material properties. Extending the methodologies to high frequency modulation provides a route to controlled, bidirectional modification to material properties, expanding the range of material functionality and opening new possibilities for future developments in fields as disparate as magnetic control, spintronics, and magnonics.

Ultrafast optical techniques provide one manner in which elastic and magnetic dynamics can be controlled in a material, since ultrafast pulses of light are known to excite elastic deformations while also modifying the magnetic properties of the material. Optically generated elastic waves can routinely achieve the frequency range of GHz with wavelength ranges of a few micrometers, which interestingly overlaps almost perfectly with similar wavelength spin waves.

In our work, we first explored the emergence of a transient magnonic crystal after the impulsive excitation of transient grating and the phase-locked elastic wave capable of preferentially driving precessional motion in different regions of the material. Secondly we have demonstrated the first instance of elastically and parametrically driven ferromagnetic oscillator, which exhibited sum and difference frequency conversion over a wide range of frequencies. Finally, we approached magnetoelastic effects from a different point of view: the study of magnetoelastic dynamics in Ni nanowires. Connecting these experiments provide possible applications in optomagnonics research which currently utilizes artificially textured materials.