title: Generation and detection of phase-coherent current-driven magnons in magnetic multilayers
abstract: The magnetic state of a ferromagnet can affect the electrical transport properties of the material; for example, the relative orientation of the magnetic moments in magnetic multilayers underlies the phenomenon of giant magnetoresistance. The inverse effect--in which a large electrical current density can perturb the magnetic state of a multilayer--has been predicted and observed experimentally with point contacts and lithographically patterned samples. Some of these observations were taken as indirect evidence for current-induced excitation of spin waves, or 'magnons'. Here we probe directly the high-frequency behaviour and partial phase coherence of such current-induced excitations, by externally irradiating a point contact with microwaves. We determine the magnon spectrum and investigate how the magnon frequency and amplitude vary with the exciting current. Our observations support the feasibility of a spin-wave maser' or 'SWASER' (spin-wave amplification by stimulated emission of radiation).
authors.affiliation: Grenoble High Magnetic Field Laboratory, Max-Planck-Institut fur Festkorperforschung and Centre National de la Recherche Scientifique, France. tsoim@labs.polycnrs-gre.fr
authors.initials: M
authors.lastname: Tsoi
authors.initials: AG
authors.lastname: Jansen
authors.initials: J
authors.lastname: Bass
authors.initials: WC
authors.lastname: Chiang
authors.initials: V
authors.lastname: Tsoi
authors.initials: P
authors.lastname: Wyder