TY  - JOUR
AU  - Jia, Hongying
AU  - Zimmermann, Bernd
AU  - Hoffmann, Markus
AU  - Sallermann, Moritz
AU  - Bihlmayer, Gustav
AU  - Blügel, Stefan
TI  - Material systems for FM-/AFM-coupled skyrmions in Co/Pt-based multilayers
JO  - Physical review materials
VL  - 4
IS  - 9
SN  - 2475-9953
CY  - College Park, MD
PB  - APS
M1  - FZJ-2020-03143
SP  - 094407
PY  - 2020
AB  - Antiferromagnetically coupled magnetic skyrmions are considered ideal candidates for high-density information carriers. This is due to the suppressed skyrmion Hall effect compared to conventional skyrmions and a smaller size due to the cancellation of some contributions to the  magnetostatic dipolar fields. By means of systematic first-principles calculations based on  density functional theory we search for suitable materials that can host antiferromagnetically coupled skyrmions. We concentrate on fcc-stacked (111)-oriented metallic $Z$/Co/Pt ($Z=4d$ series:  Y$-$Pd, the noble metals: Cu, Ag, Au, post noble metals: Zn and Cd)  magnetic multilayers of films of monatomic thickness. We present quantitative trends of magnetic properties: magnetic moments, interlayer exchange coupling,  spin stiffness, Dzyaloshinskii-Moriya interaction, magnetic anisotropy, and the critical temperature.  We show that some of the $Z$ elements (Zn, Y, Zr, Nb, Tc, Ru, Rh, and Cd) can induce antiferromagnetic interlayer coupling between the magnetic Co layers, and that they influence the easy magnetization axis. Employing a multiscale approach, we transfer the micromagnetic parameters determined from $ab$ $initio$ to a micromagnetic energy functional and search for one-dimensional spin-spiral solutions and two-dimensional skyrmions. We determine the skyrmion radius by numerically solving the equation of the skyrmion profile. We found an analytical expression for the skyrmion radius that covers our numerical results and is valid for a large  regime of micromagnetic parameters. Based on this expression we have proposed a model that allows to extrapolate from the $ab$ $initio$ results of monatomic films to multilayers with Co films consisting of several atomic layers containing 10-nm skyrmions. We found thickness regimes where tiny changes of the film thickness may alter the skyrmion radius by orders of magnitude. We estimated the skyrmion size as function of temperature and found that the size can easily double  going from cryogenic to room temperature.  We suggest promising material systems for ferromagnetically and antiferromagnetically coupled spin-spiral and skyrmion systems.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000573307600005
DO  - DOI:10.1103/PhysRevMaterials.4.094407
UR  - https://juser.fz-juelich.de/record/884244
ER  -