Stabilization of zero-field skyrmions in synthetic antiferromagnetic multilayers

Magnetic skyrmions (Sks) are topologically protected spin structures that exist at room temperature (RT) in multilayer (ML) magnetic films[1,2]. While Sks have promising current-driven motion in racetrack geometry, skyrmion Hall effect (SkHE) induced transverse deflection is an obstacle in fulfilling memory and computing applications[3]. Fortunately, antiferromagnetically (AF) coupled Sks do not exhibit SkHE[4], but conclusive experimental verifications of AF Sks in ML systems remain elusive.
This work demonstrates the field-free stabilization of synthetic AF (SAF) Sks at RT mediated by a Ir heavy metal spacer between ferromagnetic (FM) Ir/Fe/Co/Pt MLs.
With quantitative magnetic force microscopy (MFM) and micromagnetic simulations, we observe SAF character in ZF stabilized spin textures, including skyrmions. At higher magnetic fields, the textures uncouple across layers into distinct spatial regions. To add, the uncoupled textures and FM ML Sks are larger than the ZF SAF Sks. Our work establishes a ML platform for hosting SAF Sks at ZF, and is the first step towards their incorporation in skyrmionic devices.
1. A.Fert et al.,Nat.Rev.mater.2,17031(2017)
2. A.Soumyanarayanan et al.,Nat.Mater.16,898(2017)
3. A.K.C.Tan*, P.Ho* et al.,(2020,In Prep)
4. X.Zhang et al.,Nat.Comm.7,10293(2016)