Co- and contra-directional vertical coupling between ferromagnetic layers with grating for short-wavelength spin wave generation

Abstract

The possibility to generate short spin waves (SWs) is of great interest in the field of magnonics nowadays. We present an effective and technically affordable way of conversion of long SWs, which may be generated by conventional microwave antenna, to the short, sub-micrometer waves. It is achieved by grating-assisted resonant dynamic dipolar interaction between two ferromagnetic layers separated by some distance. We analyze criteria for the optimal conversion giving a semi-analytical approach for the coupling coefficient. We show by the numerical calculations the efficient energy transfer between layers which may be either of co-directional or contra-directional type. Such a system may operate either as a short spin wave generator or a frequency filter, moving forward possible application of magnonics. permalloy (Py)-CoFeB bilayer separated by a nonmagnetic spacer, with Py layer decorated with a grating. We show, that it is possible to achieve complete SW power exchange between the layers, if the structure is optimized for resonant, phase-matched interaction of a proper magnitude. We tested influence of damping on the SW energy exchange between layers, and show that the effect can be optimized by increasing grating thickness. We propose such a system to be a simple and efficient transducer for generation of short SWs in Py from long SWs in CoFeB, which allows to transfer the SW signals in the vertical direction, and also to exploit it as a narrow band filters for future magnonic devices.

Experimental Realization of a Passive Gigahertz Frequency‐Division Demultiplexer for Magnonic Logic Networks

“…Spin waves offer many advantages for wave‐based computing due to their micro‐ to nanometer small wavelengths at gigahertz frequencies, their enormous tunability by various parameters and the possibility of chargeless information transport. One exceptional property utilized in the following work is the anisotropic propagation of spin waves in suitable magnetic media, which can lead to the creation of narrow spin‐wave beams and caustics (see Experimental Section).…”

Nonresonant amplification of spin waves through interface magnetoelectric effect and spin-transfer torque

“…Both modes have almost completely uniform amplitude through each layer thickness. Note, that for the modes in Fe and Co are independent since there is no dipolar coupling between the layers in this case 36 . The higher-order modes are in the teraherz range.…”

Resonant subwavelength control of the phase of spin waves reflected from a Gires–Tournois interferometer

“…( 19 ), as described in Refs. 34 , 35 . At the edges of the computational domain (far from the ferromagnetic materials) the Dirichlet boundary conditions, forcing the magnetic potential to vanish, are imposed.…”