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Physics & Astronomy Colloquium – Spring 2019 – Barsukov
March 27 @ 3:30 pm - 5:00 pm
Speaker: Igor Barsukov (UC Riverside)
Title: Magnon condensation and exchange-mediated spin flows in magnetic heterostructures
Abstract: Injection of a pure spin current into magnetic insulator modifies the chemical potential of magnons and can lead to intriguing phenomena such as long-range spin transport and magnon condensation. We study nanowires fabricated from a bilayer of a metallic ferromagnet and an insulating ferrimagnet. Via interlayer exchange coupling, magnons can be thermally transferred from one layer into another, constituting a pure spin current. The injected incoherent magnons transfer their angular momentum to a low-energy magnon state, thereby reducing its effective damping. Above critical thermal spin current, the magnon system undergoes a phase transition establishing a coherent low-energy state. This process corresponds to bosonic condensation of non-equilibrium magnons into a magnon condensate and manifests through microwave emission from the nanowire. The design of bi-magnetic heterostructures further offers opportunities for realization of exchange-mediated spin flows over macroscopic distances (also known as spin superfluids). Using micromagnetic simulations, we investigate the impact of dipolar interactions and soliton formation in the heterostructures. We find a surprising interaction of the exchange-mediated spin flows with incoherent magnons that stabilizes the long-range spin transport.
[Parts of this work were supported by Spins and Heat in Nanoscale Electronic Systems (SHINES), an Energy Frontier Research Center funded by the US Department of Energy and by NSF under grant ECCS-1810541.]
Speaker Biography: Igor Barsukov graduated with Diploma in Physics from Ruhr-University Bochum (Germany). He commenced his graduate studies at the Academy of Sciences in Prague (Czechia) as recipient of the Marie-Curie Fellowship and obtained the PhD degree from the University Duisburg-Essen (Germany). As postdoctoral researcher, he moved to UC Irvine. In 2016, he joined the Department of Physics and Astronomy at UC Riverside as Assistant Professor. His lab focuses on experimental condensed matter physics, in particular on spintronics. The research interests include microwave and terahertz spectroscopy, spin transport, nonlinear spin dynamics, and thermodynamics of magnetic systems.