Zero-field Fiske resonance coupled with spin-waves in ferromagnetic Josephson junctions

強磁性ジョセフソン接合におけるスピン波と結合したゼロ磁場フィスケ共鳴

挽野 真一*; 森 道康  ; 前川 禎通

Hikino, Shinichi*; Mori, Michiyasu; Maekawa, Sadamichi

AC Josephson current in a Josephson junction with voltage bias is spatially modulated by an external magnetic field, and induces an electromagnetic (EM) field inside the junction. The current-voltage (I-V) curve exhibits peaks due to the resonance between the EM field and the spatially modulated AC Josephson current. This is called . Such a spatially modulated Josephson current can be also induced by a non-uniform insulating barrier and the Fiske resonance appears without external magnetic field. This is called zero-field Fiske resonance (ZFFR). In this paper, we theoretically study the ZFFR coupled with spin-waves in a superconductor/ferromagnetic insulator/superconductor junction (ferromagnetic Josephson junction) with a non-uniform ferromagnetic insulating barrier. The resonant mode coupled with spin-waves can be induced without external magnetic field. We find that the I-V curve shows resonant peaks associated with composite excitations of spin-waves and the EM field in the junction. The voltage at the resonance is obtained as a function of the normal modes of EM field. We show several current-density dependences of the ZFFRs coupled with spin-waves.