Magnonics: spin waves connecting charges, spins and photons

Spin waves (SW) are the excitation of the spin system in a ferromagnetic condensed matter body. They are collective excitations of the electron system and, from a quasi-classical point of view, can be understood as a coherent precession of the electrons’ spins. Analogous to photons, they are also referred to as magnons indicating their quasi-particle character. The collective nature of SWs is established by the short-range exchange interaction as well as the non-local magnetic dipolar interaction, resulting in coherence of SWs from mesoscopic to even macroscopic length scales. The possibilities of SWs being a new means of information carriers stimulated the emerging research field called ‘magnonics’. The field of modern magnonics is very wide and covers a variety of emerging physical phenomena. One of the important part of the field of magnonics occupies investigations of magnonic crystals, which are artificial magnetic materials with properties periodically varied in space.