Tuning magnonic devices with on-chip permanent micromagnets

TL;DR

This paper demonstrates a novel on-chip micromagnet approach to tune magnonic devices, enabling low-power, integrated control of spin-wave propagation without bulky electromagnets.

Contribution

It introduces a method using permanent micromagnets to achieve tunable spin-wave properties in magnonic devices, replacing traditional bulky magnetic field sources.

Findings

Tunable transverse bias field between 3.0 and 7.5 mT achieved

Attenuation length and phase shift of spin waves can be controlled

Micromagnet configuration enables low-power device operation

Abstract

One of the most appealing features of magnonics is the easy tunability of spin-waves propagation via external magnetic fields. Usually this requires bulky and power-hungry electromagnets which are not compatible with device miniaturization. Here we propose a different approach, exploiting the stray field from permanent micromagnets integrated on the same chip of a magnonic wave-guide. In our monolithic device, we employ two SmCo square micromagnets (10x10 $\mu$m$^2$) flanking a CoFeB conduit at different distances from its axis, to produce a tunable transverse bias field between 7.5 and 3.0 mT in the conduit region between the magnets. Spin waves excited by an antenna just outside the region between the magnets enter a region with a variable higher (lower) effective field when an external bias field is applied parallel (antiparallel) to that from the micromagnets. Consequently, the attenuation length and phase shift of Damon-Eshbach spin waves can be tuned in a wide range by playing with the parallel-antiparallel configuration of the external bias and the distance between SmCo micromagnets and the CoFeB conduit. This work demonstrates the potential of permanent micro-magnets for the realization of low-power, integrated magnonic devices with tunable functionalities.