From 2D Planar Magnonic Crystals to 3D Magnonic Crystals

Magnetic films with a periodic pattern were considered for controlling spin waves (SWs) from 1976. The concept of magnonic crystals (MCs) was proposed as an SW counterpart of photonic crystals. The MC can be formed from a magnetic material with periodic distribution of the constituent materials or periodic modulation of some magnetic parameters or other parameters relevant to the propagation of SWs, such as the external magnetic field, geometry, temperature, or a surrounding of the homogeneous ferromagnetic medium. The chapter provides an overview of the theoretical results on the magnonic band structure in three-dimensional (3D) MCs. The most challenging problem related to experimental studies on 3D MCs is the fabrication of a high-quality structure with periodicity along three directions in the nanoscale. The research on 3D MCs was concentrated on the calculation of the magnonic band structure and influence of the material and geometrical parameters on the magnonic bandgaps. The chapter concludes with prospects for further development toward 3D MCs.