Composite Excitation of Josephson Phase and Spin Waves in Josephson Junctions with Ferromagnetic Insulator

概要

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Coupling of Josephson-phase and spin-waves is theoretically studied in a superconductor/ferromagnetic insulator/superconductor (S/FI/S) junction. Electromagnetic (EM) field inside the junction and the Josephson current coupled with spin-waves in FI are calculated by combining Maxwell and Landau--Lifshitz--Gilbert equations. In the S/FI/S junction, it is found that the current--voltage (I--V) characteristic shows two resonant peaks for each mode of the EM field. Voltages at the resonant peaks are obtained as a function of the normal modes of EM field, which indicates a composite excitation of the EM field and spin-waves in the S/FI/S junction. We also examine another type of junction, in which a nonmagnetic insulator (I) is located at one of interfaces between S and FI. In such a S/I/FI/S junction, three resonant peaks appear in the I--V curve, since the Josephson-phase couples to the EM field in the I layer.
2011-07-15