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Phase-coherent current-driven magnons in magnetic multilayers |
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| Authors: | M Tsoi |
| Institution: | a Department of Physics and Astronomy, Center for Fundamental Materials Research, and Center for Sensor Materials, Michigan State University, East Lansing, MI 48824-1116, USA b Grenoble High Magnetic Field Laboratory, Max-Planck-Institut für Festkörperforschung and Centre National de la Recherche Scientifique, B.P. 166, F-38042 Grenoble Cedex 9, France |
| Abstract: | We report the detection of electromagnetic waves radiated by current-driven magnons in a Co/Cu magnetic multilayer. The magnons were excited by means of a high current density ≈108 A/cm2 injected into the multilayer through a point contact. The point contact itself was used as a high frequency mixer to mix electromagnetic waves radiated by the current-driven magnons with externally generated microwave radiation. Here the external microwaves are used as a direct probe of the high-frequency behavior and partial phase coherence of the current-induced excitations. When the external frequency equaled the frequency of the magnons generated in the multilayer a DC voltage was found to develop across the contact. Investigation of how this voltage varies with exciting current, magnetic field, and microwave frequency provides detailed information on the spectrum of the current-driven magnons. Our observations support the feasibility of a spin-wave maser, or spin-wave amplification by stimulated emission of radiation. |
| Keywords: | Transport properties Multilayers Excitation—spin waves Electromagnetic waves |
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