Magnetic periodic structures - magneto-photonic and magnonic crystals

Abstract

Summary form only given. In the current work a new class of magnetic materials is described and analyzed. Drawing an analogy with photonic crystals possessing a photonic band, namely the frequency range where the wave propagation if completely forbidden, such magnetic media can be named magnonic crystals. Such crystals represent the magnetic medium in which the magnetic properties are varied periodically. The simplest type of the one-dimensional magnonic crystals is a multilayered periodic structure composed from the magnetic layers with the different magnetization. Spin waves propagation through this structure is prohibited within the restricted bands. It is shown that a localized spin wave mode can exist in a forbidden zone if the periodicity of the system is broken in a particular place. Such magnonic crystals in a microwave frequency range can be a challenge for photonic crystals operating at the visual light frequency band. The analysis of such systems is provided along with theoretical and numerical calculations of forbidden zones and spin wave modes. The dispersion characteristics of spin waves in such magnonic crystals are considered along with reflection and transmission of spin waves through such a structure. In particular, the one-dimensional periodic magnetic structure is considered containing magnetic layers with the same thickness but different magnetisation. The wave spectrum contains forbidden zones and the transmission coefficient from such a structure almost equal to 0, thus the wave totally reflected. Numerical calculations are provided for real multilayered structures. It is further shown that three-dimensional periodic magnetic systems can possess a full magnonic band where spin-wave propagation in a particular frequency band is prohibited in all directions. On the contrary to the photonic crystal bands the magnonic band can be tuned by the variation of the external magnetic field. The propagation of optical radiation in a magnetic waveguides with the periodic domain structures (magneto-photonic crystals) is further investigated. Two types of periodic structures are studied -one- and two-dimensional.