Current induced domain wall motion with a Ta/Gd-Fe/Si-N magnetic nanowire for a magneto-optical light modulator

Kenichi Aoshima,Kenji Machida,Nobuhiko Funabashi,Ryo Higashida

doi:10.1063/1.5130488

Kenichi Aoshima, Kenji Machida + Show 2 more

Open Access

https://doi.org/10.1063/1.5130488

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Journal: AIP Advances	Publication Date: Jan 1, 2020
Citations: 1	License type: cc-by

Affiliation: Japan Broadcasting Corporation (Japan)

Abstract

We investigated a magnetic nanowire device for a light modulator which is very important for 3D holography display application. It has a Si-N/Ta/Gd-Fe/Si-N nanowire with 0.5 × 17 μm2 dimension and a Co/Pd multilayer hard magnet with its size of 0.5 × 3 μm2 which is attached underneath the nanowire for initial domain nucleation. Both the nanowire and the hard magnet have perpendicular anisotropy. An initial domain was successfully nucleated by pulse current and found spin-orbit torque from Ta and local magnetic field from the nanomagnet was responsible for the domain nucleation. Current induced domain wall (DW) motion was observed and the DW moved along current direction without magnetic field. DW velocity was significantly enhanced with in-plane magnetic field (Hinp) of 25mT and velocity more than 200 m/s was obtained, which was more than 25 times faster than that without magnetic field. We also show that the fast DW velocity is attributed to chiral Neel domain wall induced by external in-plane magnetic field. This fast DW motion is very useful for large scale light modulator which refreshes large number of pixels, such as 10K × 10K pixels, over a limited time scale of 8 ∼ 16.7 ms which corresponds to TV frame rate of 120 or 60 Hz.

Highlights

Magneto-optical spatial light modulators (MOSLM) driven by spin-transfer switching with current-perpendicular-to-plane (CPP) devices have been developed for 3D holography display application with wide viewing zone
The fast domain wall (DW) motion is attributed to spin orbit toque (SOT) driven DW motion7–9 with chiral Neel DW structure which is promoted by Dzyaloshinsky-Moriya interaction (DMI)
One should note that DW velocity as fast as a few tens to over one hundred of m/s was obtained at the 1 mA with which showed very slow DW motion without the in-plane magnetic field

Summary

INTRODUCTION

Magneto-optical spatial light modulators (MOSLM) driven by spin-transfer switching with current-perpendicular-to-plane (CPP) devices have been developed for 3D holography display application with wide viewing zone It has successfully shown display capability with a pixel of 2 × 2 μm2.1–3 A pixel pitch of the SLM as small as 1 μm enabled large viewing angle as wide as 30 degrees, which is very important for 3D spatial images though none of the current SLM achieved so far.. The driving current for the one μm pixel with the CPP device was more than the capability of a cell selection transistor with 1μm pixel pitch, and further reduction of driving current has been pursued One solution for this issue is current in-plane type MO light modulator, which uses current-induced domain wall motion (CIDWM) to switch the magnetization direction.. In this article we investigate a Ta/Gd-Fe nanowire with a hard magnet (HM), and show a peculiar domain nucleation and velocity of CIDWM over 200 m/s

SAMPLE PREPARATION AND DEVICE FABRICATION

INITIAL DOMAIN NUCLEATION

CURRENT INDUCED DOMAIN WALL MOTION

CONCLUSION