Thermal Stability of an Interface-Stabilized Skyrmion Lattice

Sonntag, A.; Hermenau, Jan; Krause, Stefan; Wiesendanger, R.

doi:10.1103/physrevlett.113.077202

Cited by 49 publications

(40 citation statements)

References 14 publications

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“…The resulting spin texture, supplemental Fig. S4, and the transition temperature of T c = 37 K are in good agreement with previous theoretical and experimental investigations [6,24].…”

supporting

confidence: 90%

Skyrmions at the Edge: Confinement Effects in Fe/Ir(111)

et al. 2016

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We have employed spin-polarized scanning tunneling microscopy and Monte-Carlo simulations to investigate the effect of lateral confinement onto the nanoskyrmion lattice in Fe/Ir(111). We find a strong coupling of one diagonal of the square magnetic unit cell to the close-packed edges of Fe nanostructures. In triangular islands this coupling in combination with the mismatching symmetries of the islands and of the square nanoskyrmion lattice leads to frustration and triple-domain states. In direct vicinity to ferromagnetic NiFe islands, the surrounding skyrmion lattice forms additional domains. In this case a side of the square magnetic unit cell prefers a parallel orientation to the ferromagnetic edge. These experimental findings can be reproduced and explained by Monte-Carlo simulations. Here, the single-domain state of a triangular island is lower in energy, but nevertheless multi-domain states occur due to the combined effect of entropy and an intrinsic domain wall pinning arising from the skyrmionic character of the spin texture.Magnetic skyrmions are particle-like states [1] which can occur in magnetic systems with broken inversion symmetry due to the Dzyaloshinskii-Moriya interaction [2,3]. Skyrmions can either form lattices at certain field ranges [4-10] or they can be created and manipulated individually [9], thereby offering great potential for data storage, transfer and processing [11,12]. Since the geometric layout is an essential part of a device, theoretical investigations explored the effect of boundaries and confinement in skyrmionic systems [13,14]. For instance, skyrmion movement in racetracks [12] and the effect of notches [15] on their trajectories were studied and lateral confinement was suggested as a means to stabilize skyrmions without an external magnetic field [16]. However, the relative orientation of skyrmion lattices in regard to the geometry of the boundary of magnetic systems is still an open question. Most experiments focused on extended films and on their temperature and fielddependence while finite size effects were explored only very recently, e.g. in nanostripes [17] or in disk-shaped structures [18,19].Here, we employ spin-polarized scanning tunneling microscopy (SP-STM) and Monte-Carlo (MC) simulations to investigate the effect of two types of boundaries onto the nanoskyrmion lattice in the Fe atomic monolayer on Ir(111). This skyrmion lattice has four-fold symmetry, a period of about 1 nm, and exists already in zero field due to the four-spin interaction [6]. At T = 4.2 K it is insensitive to fields of up to 9 Tesla [20], which shows that it has a vanishing net moment. In extended films, three rotational domains can be found [6], where a diagonal of the magnetic unit cell aligns with one of the three symmetry equivalent close-packed atomic rows of the hexagonal Fe layer. Our new data show that at a close-packed edge of an Fe nanostructure, one diagonal of the magnetic unit cell is preferentially oriented parallel to the edge, i.e. the edge selects one of the three rotational ...

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“…The resulting spin texture, supplemental Fig. S4, and the transition temperature of T c = 37 K are in good agreement with previous theoretical and experimental investigations [6,24].…”

supporting

confidence: 90%

Skyrmions at the Edge: Confinement Effects in Fe/Ir(111)

et al. 2016

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“…This polar distortion leads to a special DMI pattern, the prerequisite of Néel-type SkLs 21, 24, 26, 38 , and a uniaxial magnetic anisotropy 42, 43 . A similar DMI pattern is realized in ultra thin magnetic layers and multilayers near the interfaces 5, 6, 10, 13, 19 . Very recently, Fujima and coworkers have indeed reported the possible emergence of modulated magnetic phases in GaV 4 Se 8 48 .…”

Section: Introductionsupporting

confidence: 53%

Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet

Bordács

Butykai

Szigeti

et al. 2017

Sci Rep

119

149

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The skyrmion lattice state (SkL), a crystal built of mesoscopic spin vortices, gains its stability via thermal fluctuations in all bulk skyrmion host materials known to date. Therefore, its existence is limited to a narrow temperature region below the paramagnetic state. This stability range can drastically increase in systems with restricted geometries, such as thin films, interfaces and nanowires. Thermal quenching can also promote the SkL as a metastable state over extended temperature ranges. Here, we demonstrate more generally that a proper choice of material parameters alone guarantees the thermodynamic stability of the SkL over the full temperature range below the paramagnetic state down to zero kelvin. We found that GaV4Se8, a polar magnet with easy-plane anisotropy, hosts a robust Néel-type SkL even in its ground state. Our supporting theory confirms that polar magnets with weak uniaxial anisotropy are ideal candidates to realize SkLs with wide stability ranges.

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“…As a comparison, the ordering temperature reported for the similar system Fe/Ir(111) in Ref. [54] is T c ≈ 28 K. Although this is lower even than the extrapolated value of T c ≈ 50 K, it is known from ab initio calculations [20,21] that the exchange interactions determining the ordering temperature are significantly weaker in the absence of the Pd overlayer.…”

Section: Skyrmion Lifetime In the Fluctuation-disordered Statementioning

confidence: 78%

Complex magnetic phase diagram and skyrmion lifetime in an ultrathin film from atomistic simulations

Rózsa¹,

Simon²,

Palotás³

et al. 2016

Phys. Rev. B

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We determined the magnetic B − T phase diagram of PdFe bilayer on Ir(111) surface by performing Monte Carlo and spin dynamics simulations based on an effective classical spin model. The parameters of the spin model were determined by ab initio methods. At low temperatures we found three types of ordered phases, while at higher temperatures, below the completely disordered paramagnetic phase, a large region of the phase diagram is associated with a fluctuation-disordered phase. Within the applied model, this state is characterized by the presence of skyrmions with finite lifetime. According to the simulations, this lifetime follows the Arrhenius law as a function of temperature.

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Thermal Stability of an Interface-Stabilized Skyrmion Lattice

Cited by 49 publications

References 14 publications

Skyrmions at the Edge: Confinement Effects in Fe/Ir(111)

Skyrmions at the Edge: Confinement Effects in Fe/Ir(111)

Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet

Complex magnetic phase diagram and skyrmion lifetime in an ultrathin film from atomistic simulations

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