Isolated zero field sub-10 nm skyrmions in ultrathin Co films

Meyer, S.; Perini, Marco; Malottki, Stephan von; Kubetzka, André; Wiesendanger, R.; Bergmann, Kirsten; Heinze, Stefan

doi:10.1038/s41467-019-11831-4

Cited by 106 publications

(104 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On an average, we notice an increase in barrier height of nearly 100 meV for skyrmions upon including the HOI. At low fields up to B − B c = 1.36 T, there is a transition from the normal radial collapse mechanism 22,34 without HOI to a chimera collapse mechanism 16,50 with HOI. Above B − B c = 1.36 T, the skyrmions merge into the FM background through the normal radial collapse without HOI, which remains unchanged after including HOI.…”

Section: Resultsmentioning

confidence: 97%

“…Due to the possibility of varying film composition and structure, these systems allow to modify magnetic interactions and thereby the properties of skyrmions. At such transition-metal interfaces, individual magnetic skyrmions with diameters ranging from a few 100 nanometers down to a few nanometers have been realized as a metastable state in the field-polarized ferromagnetic background 8,[10][11][12][13][14][15][16] as needed for applications.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Role of higher-order exchange interactions for skyrmion stability

et al. 2020

Self Cite

View full text Add to dashboard Cite

Transition-metal interfaces and multilayers are a promising class of systems to realize nanometer-sized, stable magnetic skyrmions for future spintronic devices. For room temperature applications, it is crucial to understand the interactions which control the stability of isolated skyrmions. Typically, skyrmion properties are explained by the interplay of pair-wise exchange interactions, the Dzyaloshinskii-Moriya interaction and the magnetocrystalline anisotropy energy. Here, we demonstrate that higher-order exchange interactions – which have so far been neglected – can play a key role for the stability of skyrmions. We use an atomistic spin model parametrized from first-principles and compare three different ultrathin film systems. We consider all fourth-order exchange interactions and show that, in particular, the four-site four spin interaction has a large effect on the energy barrier preventing skyrmion and antiskyrmion collapse into the ferromagnetic state. Our work opens perspectives to stabilize topological spin structures even in the absence of Dzyaloshinskii-Moriya interaction.

show abstract

Section: Resultsmentioning

confidence: 97%

mentioning

confidence: 99%

Role of higher-order exchange interactions for skyrmion stability

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Based on first-principles calculations, it has been explained that the transition from a skyrmion lattice to isolated skyrmions is due to the modification of the exchange interactions rather than the Dzyaloshinskii-Moriya interaction 15,16 . Recently, it has been demonstrated that a similar frustration of exchange interactions along with the Dzyaloshinskii-Moriya interaction can induced zero-field skyrmions in Rh/Co bilay-ers on the Ir(111) surface 17 .…”

Section: Introductionmentioning

confidence: 99%

Tailoring magnetic interactions in atomic bilayers of Rh and Fe on Re(0001)

Paul

Heinze

2020

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

Using density functional theory, we investigate the interplay among the sequence of bilayers composed of an Fe and a Rh layer on the Re(0001), their stacking order and their magnetic properties. We find that bilayers in which both layers are in fcc stacking are energetically very unfavorable, while all other combinations of hcp and fcc stacking are energetically relatively close. The magnetic interactions are evaluated by mapping the DFT energies onto an atomistic spin model, which contains the Heisenberg exchange, the Dzyaloshinskii-Moriya interaction (DMI), the magnetocrystalline anisotropy energy, and higher-order exchange interactions. We find that the stacking sequence of the bilayer significantly modifies the magnetic interactions. For bilayers in which Fe is the topmost layer, the nearest-neighbor exchange interaction is ferromagnetic, but varies in strength by a factor of up to three for different stacking sequences. The DMI even changes up to a factor of four. As a result, we find a DMI driven cycloidal spin spiral ground state with a period of 11 nm for hcp-Fe/hcp-Rh/Re(0001). For fcc-Fe/hcp-Rh/Re(0001) and hcp-Fe/fcc-Rh/Re(0001), we obtain a ferromagnetic ground state. The spin spiral energy dispersion of hcp-Fe/hcp-Rh/Re(0001) including spin-orbit coupling suggests that isolated skyrmions can be stabilized in the field-polarized ferromagnetic background at external magnetic fields. If the Fe layer is sandwiched between the Rh overlayer and the Re(0001) substrate, there is a competition between the ferromagnetic coupling preferred by the Rh-Fe hybridization and the antiferromagnetic coupling induced by the Fe-Re hybridization. Due to the Fe/Re interface, the DMI can become very large. For fcc-Rh/hcp-Fe/Re (0001), we obtain a cycloidal spin spiral with a period of 1.7 nm, which is induced by frustration of exchange interactions and further stabilized by the DMI. For hcp-Rh/hcp-Fe/Re(0001), we find a DMI driven cycloidal spin spiral with a period of 4 nm and locally nearly antiparallel magnetic moments due to antiferromagnetic nearest-neighbor exchange. The higher-order exchange constants can be significant in the considered films, however, they do not stabilize multi-Q states.

show abstract

“…[ 18 ] Extensive research into skyrmions and their dynamics near room temperature (RT) in ferromagnets has greatly extended their use in spintronic devices because of their robust thermal stability and tunability. [ 19–25 ] However, the skyrmion Hall effect (SkHE), observed as a deflection with respect to the current direction, leads to the lateral accumulation and annihilation of skyrmions, [ 26 ] which greatly hinders ferromagnetic skyrmion‐based applications. These fundamental limitations are being addressed by investigating the behavior of skyrmions in ferrimagnets and antiferromagnets.…”

Section: Figurementioning

confidence: 99%

Magnetic Skyrmions in a Hall Balance with Interfacial Canted Magnetizations

Zhang

Gao

et al. 2020

Advanced Materials

View full text Add to dashboard Cite

Magnetic skyrmions are attracting interest as efficient information‐storage devices with low energy consumption, and have been experimentally and theoretically investigated in multilayers including ferromagnets, ferrimagnets, and antiferromagnets. The 3D spin texture of skyrmions demonstrated in ferromagnetic multilayers provides a powerful pathway for understanding the stabilization of ferromagnetic skyrmions. However, the manipulation mechanism of skyrmions in antiferromagnets is still lacking. A Hall balance with a ferromagnet/insulating spacer/ferromagnet structure is considered to be a promising candidate to study skyrmions in synthetic antiferromagnets. Here, high‐density Néel‐type skyrmions are experimentally observed at zero field and room temperature by Lorentz transmission electron microscopy in a Hall balance (core structure [Co/Pt]n/NiO/[Co/Pt]n) with interfacial canted magnetizations because of interlayer ferromagnetic/antiferromagnetic coupling between top and bottom [Co/Pt]n multilayers, where the Co layers in [Co/Pt]n are always ferromagnetically coupled. Micromagnetic simulations show that the generation and density of skyrmions are strongly dependent on interlayer exchange coupling (IEC) and easy‐axis orientation. Direct experimental evidence of skyrmions in synthetic antiferromagnets is provided, suggesting that the proposed approach offers a promising alternative mechanism for room‐temperature spintronics.

show abstract

Isolated zero field sub-10 nm skyrmions in ultrathin Co films

Cited by 106 publications

References 56 publications

Role of higher-order exchange interactions for skyrmion stability

Role of higher-order exchange interactions for skyrmion stability

Tailoring magnetic interactions in atomic bilayers of Rh and Fe on Re(0001)

Magnetic Skyrmions in a Hall Balance with Interfacial Canted Magnetizations

Contact Info

Product

Resources

About