Bloch-type magnetic skyrmions are nanoscale vortex-like spin objects that form densely packed lattice arrangements in B20-type chiral magnets in the presence of a magnetic field. Here, we use off-axis electron holography, in combination with an iterative model-based reconstruction algorithm, to study the geometries of the projected in-plane magnetization distributions of individual skyrmions in an FeGe thin film as a function of applied magnetic field. We compare our results with micromagnetic simulations and find a departure from magnetic chirality in the transition regions between adjacent skyrmions when they are in lattice arrangements.

An external electric field can modify the strength of the spin-orbit interaction between spins of ions in magnetic crystals. This influence leads to a spin-wave frequency shift that is linear in both the applied electric field and the wave vector of the spin wave. Here we study theoretically the external electric field as a means of control of the spin-wave power flow in thin ferromagnets. The spin-wave group velocity and focusing patterns are obtained from the slowness (isofrequency) curves by evaluating their curvature at each point of the reciprocal space. We show that the combination of the magnetodipole interaction and the electric field can result in nonreciprocal unidirectional caustic beams of dipole-exchange spin waves. We demonstrate that the degree of asymmetry of the spin-wave power flow can be tuned with the external electric field. Our findings open a novel avenue for spin-wave manipulation and development of electrically tunable magnonic devices.

No abstract

External electric field can modify the strength of the spin-orbit interaction between spins of ions in magnetic crystals. This influence leads to a spin wave frequency shift that is linear in both the applied electric field and the wave vector of the spin wave. Here, we explore theoretically the external electric field as a means of control of the spin wave power flow in ultrathin ferromagnets. The spin wave group velocity and focusing pattern is obtained from the slowness (isofrequency) curves by evaluating their curvature at each point of the reciprocal space. We show that the combination of the magneto-dipole interaction and the electric field can result in non-reciprocal unidirectional caustic beams of dipole-exchange spin waves. Our findings open a novel avenue for spin wave manipulation and development of electrically tuneable magnonic devices.