Ferromagnetic resonance and the dynamics of the magnetic moment in a “Josephson junction–nanomagnet” system

The dynamics of a nanomagnet coupled to a Josephson junction has been studied. Although a magnetic field induced by the superconducting current in the Josephson junction is very weak, an applied voltage can generate the nonlinear dynamics of the nanomagnet, which gives a number of interesting phenomena. It has been shown that a ferromagnetic resonance can occur when the frequency of Josephson oscillations becomes equal to the eigenfrequency of the magnetic system. It has been demonstrated that the easy axis of the nanomagnet is reoriented at an increase in the Josephson-to-magnetic energy ratio, as well as in the coupling parameter between the Josephson current and the magnetic moment and in the frequency of Josephson oscillations. It has been shown that a current pulse can turn the magnetic moment of the nanomagnet, which opens new prospects for the application of this system in superconducting spintronics.