Creation of nanometric magnetic skyrmions by global application of circularly polarized microwave magnetic field

Abstract

From a theoretical perspective, we demonstrate that nanometric magnetic skyrmions are created by application of a circularly polarized microwave magnetic field to a thin-plate Dzyaloshinskii-Moriya ferromagnet with fabricated rectangular holes. This phenomenon is caused by an effective steady magnetic field perpendicular to the microwave-polarization plane induced by the rotating magnetic field and the intense interference of spin waves excited by this magnetic field due to the hole structure, which causes reversals of local magnetizations and results in the formation of skyrmions. Our proposal provides a new option to write or create magnetic textures the sizes of which are much smaller than the spot size of the external stimulus such as magnetic field, light, and microwave.

Dynamical Switching of Magnetic Topology in Microwave-Driven Itinerant Magnet

“…In the meanwhile, the counterclockwise circularly po-larized microwave field considered in the present study generates an effective static magnetic field perpendicular to the polarization plane −ωe z [77,98]. Therefore, a perpendicular component of the total magnetic field is…”

“…To discuss the phase diagram in Fig. 5, we should first note that a circularly polarized microwave field generates an effective static magnetic field ±ωe z perpendicular to the polarization plane [77,98]. The amplitude is equal to ω (i.e., ω/gµ B in real units), while the sign is determined by the sense of the circular polarization, i.e., positive (negative) for the clockwise (counterclockwise) polarization.…”

“…Thereby, their low-energy excitations and continuous variations are possible, which provide us a unique opportunity to control and switch the magnetic topology with an external stimulus such as static magnetic field, electric currents [56], and microwave magnetic field. It has been revealed that topological magnetisms such as skyrmions and skyrmion tubes in chiral magnets have peculiar collective modes or spin-wave modes at microwave frequencies [57][58][59][60][61][62], and they have turned out to cause interesting physical phenomena and potential device functions [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79]. We expect that the topological magnetisms in centrosymmetric magnets can also host interesting dynamical phenomena and functionalities associated with their microwave-active collective modes.…”

Spin-wave focusing induced skyrmion generation

“…The idea is as follows: First, the spin-wave intensity near the focal point can be significantly enhanced, so that the nonlinear effect becomes dominating; Second, the focal-point magnetization oscillates strongly and might even be locally reversed, which is necessary for the nucleation of magnetic skyrmion. In this letter, we demonstrate that skyrmions can be created by spin-wave focusing in a magnetic film without introducing external defects as the nucleation sites [27][28][29] . To achieve a perfect focusing without spherical aberration 26 , we design a spinwave lens with a curved interface [see Eq.…”

Archimedean screw in driven chiral magnets

“…This mechanism is absent for the topologically trivial helical and conical phases, which are therefore more difficult to control. It has also been suggested to use oscillating fields to move a single skyrmion [8][9][10], to create skyrmions [11] or to melt skyrmion crystals [12]. Similarly, the motion of domain walls by oscillating fields has been studied in simulations [13].…”