EXPERIMENTAL AND THEORETICAL STUDIES OF SPIN-WAVE DYNAMICS IN MAGNETIC NANOSTRUCTURES

Abstract

Spin-wave dynamics in magnetic nanostructures have been studied using Brillouin light scattering and theoretical methods. The main topics include: 1. Experimental and theoretical observation of the band structures of magnonic crystals. The excitation efficiency of external magnetic fields was studied in detail. The effect of introducing artificial defects into magnonic crystals was also investigated experimentally. 2. Different from the Heisenberg model, Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric coupling that favors canted alignment between neighbouring spins. Using BLS, direct observations of interfacial DMIs at the Pt/Co and Pt/CoFeB interfaces have been made. Their effects on the dynamics of SWs were discussed, including asymmetric band structure and lifetime. 3. Nonreciprocal spin-wave propagation is fundamental to the design of unidirectional SW-based devices. In addition to the magnetic dipole-dipole interaction, new mechanisms have been proposed to realize SW nonreciprocity: magnonic mode transition arising from a symmetry-breaking magnetic field and interfacial DMI.