Magnetoelectric Spin Wave Modulator Based On Synthetic Multiferroic Structure

Abstract

We describe a spin wave modulator – spintronic device aimed to control spin wave propagation by an electric field. The modulator consists of a ferromagnetic film serving as a spin wave bus combined with a synthetic multiferroic comprising piezoelectric and magnetostrictive materials. Its operation is based on the stress-mediated coupling between the piezoelectric and magnetostrictive materials. By applying an electric field to the piezoelectric layer, the stress is produced. In turn, the stress changes the direction of the easy axis in the magnetostrictive layer and affects spin wave transport. We present experimental data on a prototype consisting of a piezoelectric [Pb(Mg1/3Nb2/3)O3](1-x) –[PbTiO3]x substrate, and 30 nm layer of magnetostrictive Ni film, where the film is attached to a 30 nm thick Ni81Fe19 spin wave bus. We report spin wave signal modulation in Ni81Fe19 layer by an electric field applied across the piezoelectric layer. The switching between the spin wave conducting and non-conducting states is achieved by applying ±0.3 MV/m electric field. We report over 300% modulation depth detected 80 μm away from the excitation port at room temperature. The demonstration of the spin wave modulator provides a new direction for spin-based device development by utilizing an electric field for spin current control.

Electric‐Field Control of Propagating Spin Waves by Ferroelectric Domain‐Wall Motion in a Multiferroic Heterostructure

“…Propagation of spin waves along or across the gated area modifies both the spin‐wave amplitude and phase. [ 25,26,41 ] The electric‐field control mechanism reported here is different, as it does not tune the strength of magnetic anisotropy in the Fe film on top of the individual a and c domains of the BaTiO 3 substrate. Instead, the magnetic anisotropy boundaries in the multiferroic heterostructure follow the motion of ferroelectric domain walls under an applied electric field.…”

“…[ 33 ] Thus far, electric‐field control of spin waves via strain coupling has been studied primarily in systems combining a magnetic layer and a piezoelectric substrate or film. For instance, electric‐field tuning of effective magnetic damping, [ 34 ] FMR modes, [ 35–38 ] and surface modes, [ 39 ] electric‐field excitation [ 40 ] and manipulation [ 41 ] of propagating spin waves, and reconfigurable spin‐wave routing [ 42 ] have been demonstrated. In these examples, the application of an electric field across the piezoelectric layer alters the strength of magnetoelastic anisotropy within the electrode contact area of the magnetic film.…”

The effect of material defects on resonant spin wave modes in a nanomagnet

“…This indicates that spin waves are very sensitive to defects and that will cause significant device-to-device variability since the defect morphology will be different in different devices. In single (or few) device applications like magnonic holography 32 or a magnonic gate 2 or spin wave interferometer 33 or modulator 34 , this will not matter much since the number of devices involved is one or few, but in large-scale spin wave “circuits” where numerous devices have to behave in nominally identical manner for overall circuit functionality, the device-to-device variability caused by defects could be debilitating. Spin wave circuits that have little tolerance for variations of spin wave frequencies, or their power distributions, or their phase profiles – e.g.…”

Confined magnetoelastic waves in thin waveguides

“…Yet, besides recent investigations of the magnetoelastic coupling in nanoscale resonators [61][62][63][64][65], a detailed study of propagating magnetoelastic waves in nanoscale waveguides is still lacking. It is clear that a detailed understanding of confined propagating magnetoelastic waves is crucial for emerging magnonic device applications, especially where spin waves are excited by magnetoelectric means and used for information transfer and processing [41,42,66,67].…”