We study electromagnetic interaction of a nanomagnet with a weak superconducting link. Equations that govern coupled dynamics of the two systems are derived and investigated numerically. We show that the presence of a small magnet in the proximity of a weak link may be detected through Shapiro-type steps caused by the precession of the magnetic moment. Despite very weak magnetic field generated by the weak link, a time-dependent bias voltage applied to the link can initiate a nonlinear dynamics of the nanomagnet that leads to the reversal of its magnetic moment. We also consider quantum problem in which a nanomagnet interacting with a weak link is treated as a two-state spin system due to quantum tunneling between spin-up and spin-down states.

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We report numerical and analytical studies of the reversal of the magnetic moment of a singledomain magnetic particle by a circularly polarized ac field of time-dependent frequency. For the time-linear frequency sweep, the phase diagrams are computed that illustrate the dependence of the reversal on the frequency sweep rate v, the amplitude of the ac field h, the magnetic anisotropy field d, and the damping parameter α. It is shown that the most efficient magnetization reversal requires a non-linear time dependence of the frequency, ω(t), for which an exact analytical formula is derived with account of damping. The necessary condition of the reversal is h > αd. Implementation of a small-scale magnetization reversal is proposed in which a nanomagnet is electromagnetically coupled to two weak superconducting links controlled by the voltage. Dynamics of such a system is analyzed with account of the back effect of the magnet on the superconducting links.

Switching of the direction of the magnetic moment in a nanomagnet is studied within a modified Slonczewski's model that permits torsional oscillations of the magnet. We show that the latter may inhibit or assist the magnetization switching, depending on parameters. Three regimes have been studied: the switching by torsional oscillations alone, the switching by the spin-polarized current with torsional oscillations permitted, and the magnetization switching by the current combined with the mechanical twist. We show that switching of the magnetic moment is possible in all three cases and that allowing torsional oscillations of the magnet may have certain advantages for applications. Phase diagrams are computed that show the range of parameters required for the switching.

The Einstein-de Haas effect is used to study experimentally the interfacial spin transport in a bilayer metallic system. Specifically, mechanical torque on a permalloy film interfaced with a non-magnetic metallic film (platinum or copper), deposited on a microcantilever, is measured. The torque is generated by the transfer of the spin angular momentum from the permalloy film to the mechanical angular momentum of the cantilever. Measurement of the cantilever deflection shows that the presence of a thin non-magnetic metallic layer with strong spin-orbit interaction (platinum) changes the interfacial spin transport and causes a dramatic reduction of the mechanical torque. The observed behavior of the cantilever is attributed to the increased effective damping of the domain wall motion in the permalloy layer.

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