Magnonic circuits and crystals

Abstract

In the frame of the long-wavelength Heisenberg model, a simple magnonic mono-mode circuit is designed to obtain transmission stop (pass) bands where the propagation of spin waves is forbidden (allowed). This simple device is composed of an infinite one-dimensional monomode waveguide (the backbone) along which side resonators (symmetric or asymmetric loops) are grafted. These circuits are usually mono-mode when the lateral dimensions of the conducting wires are small as compared to the magnon wavelength. Their production utilizes the most advanced surface technologies and represents one of the most important challenges for the next decade. In all these circuits, the interfaces between the different wires out of which the circuits are made, play a fundamental role. All such circuits exhibit a variety of interference effects in their transport properties. Emphasis in this review article is placed on the network creations, which include stubs or resonators, closed symmetric or asymmetric loops and interconnecting branched networks. In other words, a fundamental understanding of nanoscaled materials has become an important challenge for any technical applications. For magnetic nanoparticles, the investigations are in particular stimulated by the magnetic storage devices. Then we present a theory of the magnon propagation in a quasi-one-dimensional resonant structure, composed of one nanometric magnetic cluster chain and adsorbed clusters near the chain. Results for the transmission and reflection properties of such circuits (nanometric networks) are discussed, as a function of the frequency of the excitations and the physical or geometrical properties of the circuits. In the last part of this report, we review magnonic crystals. These man-conceived materials should be useful for many applications and, in particular, for designing the mono-mode circuits reviewed in the first part of this paper. These magnonic materials and circuits may have uses for the design of integrated devices such as narrow-frequency optical or microwave filters, high-speed switches, multiplexers, storage devices, ….