Thermally activated domain-wall (DW) motion in magnetic insulators has been considered theoretically, with a particular focus on the role of Dzyaloshinskii-Moriya interaction (DMI) and thermomagnonic torques. The thermally assisted DW motion is a consequence of the magnonic spin current due to the applied thermal bias. In addition to the exchange magnonic spin current and the exchange adiabatic and the entropic spin transfer torques, we also consider the DMI-induced magnonic spin current, thermomagnonic DMI fieldlike torque, and the DMI entropic torque. Analytical estimations are supported by numerical calculations. We found that the DMI has a substantial influence on the size and the geometry of DWs, and that the DWs become oriented parallel to the long axis of the nanostrip. Increasing the temperature smoothes the DWs. Moreover, the thermally induced magnonic current generates a torque on the DWs, which is responsible for their motion. From our analysis it follows that for a large enough DMI the influence of DMI-induced fieldlike torque is much stronger than that of the DMI and the exchange entropic torques. By manipulating the strength of the DMI constant, one can control the speed of the DW motion, and the direction of the DW motion can be switched, as well. We also found that DMI not only contributes to the total magnonic current, but also it modifies the exchange magnonic spin current, and this modification depends on the orientation of the steady-state magnetization. The observed phenomenon can be utilized in spin caloritronics devices, for example in the DMI based thermal diodes. By switching the magnetization direction, one can rectify the total magnonic spin current.

Recent studies point to virtual hopping of the oxygen atoms and strong spin-orbit interaction as the source of coupling of the magnetic order of yttrium iron garnet (YIG) to an applied external electric field. As shown here, an electric field can thus be utilized for pumping magnonic spin current at structured Pt / YIG interface. A finite uniform temperature is needed to thermally activate magnons as the carriers of the spin current. This current arises thus at finite uniform temperatures, applied external electric field, and for appropriate nanostructuring. Due to the inverse spin Hall effect, the generated magnonic spin pumping current is further converted into an electric voltage. We analyze the underlaying microscopic mechanism for the generation of the spin current and demonstrate by full numerical simulations that the spin current is substantial. Effects related to static as well as time-dependent E-fields and enhanced damping are discussed. The results indicate that generally, the proposed method for generating spin currents works for magnetic insulators that respond to a moderate electric field, and that the required nanostructuring poses no obstacle making this approach highly suitable for spintronic applications.

We suggest and demonstrate via large scale numerical simulations an electrically operated spinwave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.