Injection of a pure spins current into a 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 injection generates a non-equilibrium population of incoherent magnons.
Finding new ways for fast and efficient processing and transfer of data is one the most challenging tasks nowadays. Elementary spin excitations - magnons (spin wave quanta) - open up a very promising direction of high-speed and low-power information processing . Magnons are bosons, and thus they are able to form spontaneously a spatially extended, coherent ground state, a Bose-Einstein condensate (BEC), which can be established independently of the magnon excitation mechanism even at room temperature.