Xe-PFIB microstructuring of Yttrium Iron Garnet films for quantum magnonic applications

Recently, the growing interest in quantum magnonics triggered intensive investigation of magnetic materials in the quantum limit. One of the main challenges in this area is to achieve long magnon lifetimes at cryogenic temperatures. Among all currently known magnetic materials, single-crystal Yttrium Iron Garnet (YIG, Y₃Fe₅O₁₂) possesses the lowest damping due to low spin-orbit coupling. Thin YIG films are, however, grown on GGG (Gd₃Ga₅O₁₂) substrates, which induce high magnetic damping at low temperatures [1].
Here we report on using Xenon Plasma Focused Ion Beam (Xe-PFIB) technique to prepare high-quality microstructured YIG films detached from GGG substrates. This technique allows production of relatively large (50 x 50 x 20 µm³) structures in a reasonable time of a few hours. The magnetic properties of these samples were evaluated using broadband ferromagnetic resonance spectroscopy in a wide temperature range (down to 80mK). Additional investigations were done by means of wavevector-resolved Brillouin light scattering spectroscopy. Through these techniques, we evaluate the effects of Xe-PFIB structuring on the magnetic damping.
We believe that our findings will pave the way to efficient implementation of YIG elements into hybrid quantum circuits.
[1] PRB 97, 214405 (2018)