Magnonic crystals are artificial materials with periodic modulation of the magnetic properties that have recently received special attention due to the fact that slight changes of the external field can have dramatic consequences on the information carrier (“magnon”) propagation, which can be boosted or delayed even to steadiness: in this way the same device can operate either as a memory or a waveguide. Employing the dynamical matrix method [1], we performed calculations on a squared 2D lattice of dots in the vortex state, varying the in-plane wavevector components to investigate the first Brillouin zone. We computed the dispersion relations for gyrotropic, azimuthal and radial modes. We discuss the dynamical coupling of modes with different cell wavefunctions, which is not purely dipolar as for the saturated states. We discuss how the circular polarization on the modes depends on the Bloch wavevector. We considered also the effects of application of a magnetic field, which moves the vortex core off the center of the disk: for a class of modes, propagation perpendicular to the direction of the applied field is speeded up, while parallel to the applied field is slowed down. These results can be important for designing versatile magnetic filters, in which variation of the applied field direction and intensity can turn the device from a waveguide into a memory, but also for spin logic devices, in which propagation or steadiness of the information carrier along a desired direction can be associated to different binary digits. [1] L. Giovannini, F. Montoncello, and F. Nizzoli, Phys. Rev. B 75, 024416 (2007).
Information carrier bandwidth and speed tunability in magnonic crystals in the vortex state
MONTONCELLO, Federico;GIOVANNINI, Loris
2013
Abstract
Magnonic crystals are artificial materials with periodic modulation of the magnetic properties that have recently received special attention due to the fact that slight changes of the external field can have dramatic consequences on the information carrier (“magnon”) propagation, which can be boosted or delayed even to steadiness: in this way the same device can operate either as a memory or a waveguide. Employing the dynamical matrix method [1], we performed calculations on a squared 2D lattice of dots in the vortex state, varying the in-plane wavevector components to investigate the first Brillouin zone. We computed the dispersion relations for gyrotropic, azimuthal and radial modes. We discuss the dynamical coupling of modes with different cell wavefunctions, which is not purely dipolar as for the saturated states. We discuss how the circular polarization on the modes depends on the Bloch wavevector. We considered also the effects of application of a magnetic field, which moves the vortex core off the center of the disk: for a class of modes, propagation perpendicular to the direction of the applied field is speeded up, while parallel to the applied field is slowed down. These results can be important for designing versatile magnetic filters, in which variation of the applied field direction and intensity can turn the device from a waveguide into a memory, but also for spin logic devices, in which propagation or steadiness of the information carrier along a desired direction can be associated to different binary digits. [1] L. Giovannini, F. Montoncello, and F. Nizzoli, Phys. Rev. B 75, 024416 (2007).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.