[CMT Seminar] Joe Bailey – Spin wave dynamics in ultrathin yttriumiron garnet measured with x-ray microscopy

Title: Spin wave dynamics in ultrathin yttriumiron garnet measured with x-ray microscopy

Speaker: Joe Bailey, from the PSI (Switzerland)

Time: 10:30-11am Fika / 11-12am Talk

Abstract: Magnonics, the study and development of devices utilising collective spin excitations, is a rapidly growing field, covering both fundamental topics (antiferromagnetism[1], quasiparticle condensates[2]) and technological applications (MRAM[3], spintronics[4]). Yttrium iron garnet (YIG) is a ferrimagnetic insulator with the lowest known magnon damping factor of any material [5]. This low damping leads to a prevalence of nonlinear effects and notably the room temperature Bose-Einstein condensation (BEC) of magnons first reported by Demokritov et al in 2006[6], and subject of a number of investigations since[7]-[10]. Ultrathin structures will be required for applications butremainlargelyunexplored. Here I report on the design, fabrication and characterization of microwave devicesbased on such ultrathin structures(YIG thickness~100nm).The spin wavedynamics weremeasured using both Brillouin Light Scattering (BLS) and time resolved scanning transmission x-ray microscopy(TR-STXM), locked in phase with microwave stimulation of the devices.Anumber of milestonesare reached for our novel devices.First, we have explicitly measuredthe spin wave dispersion in YIG[11], and demonstratedthe existence of the finite momentum minimum required for magnon BEC. Second, the BLSdata demonstratethat the condensate exists in our samples. These results are a key development towards addingcondensate phenomena to the thin film magnonics toolbox.