Controlled creation of nanometric skyrmions using external magnetic fields

To exploit nanometric magnetic skyrmions as information carriers in high-density storage devices, a method is needed that creates intended number of skyrmions at specified places in the device preferably at a low energy cost. We theoretically propose that using a system with a fabricated hole or notch, the controlled creation of individual skyrmions can be achieved even when using an external magnetic field applied to the entire specimen. The fabricated defect turns out to work like a catalyst to reduce the energy barrier for the skyrmion creation.Comment: 5 pages, 4 figure

Theoretically predicted picosecond optical switching of spin chirality in multiferroics

We show theoretically with an accurate spin Hamiltonian describing the multiferroic Mn perovskites that the application of the picosecond optical pulse with a terahertz frequency can switch the spin chirality through intensely exciting the electromagnons. There are four states with different spin chiralities, i.e. clockwise and counterclockwise ab/bc-plane spin spirals, and by tuning the strength, shape and length of the pulse, the switching among these states can be controlled at will. Dynamical pattern formation during the switching is also discussed.Comment: 4+ pages, 5 figure