Prediction of stable nanoscale skyrmions in monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mn>5</mml:mn></mml:msub><mml:msub><mml:mi>GeTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Dongzhe Li, Soumyajyoti Haldar, Leo Kollwitz, Hendrik Schrautzer, Moritz A. Goerzen, Stefan Heinze
Abstract
Using first-principles calculations and atomistic spin simulations, we predict stable isolated skyrmions with a diameter below 10 nm in a monolayer of the two-dimensional van der Waals ferromagnet ${\mathrm{Fe}}_{5}{\mathrm{GeTe}}_{2}$, a material of significant experimental interest. A very large Dzyaloshinskii-Moriya interaction (DMI) is observed due to the intrinsic broken inversion symmetry and strong spin-orbit coupling for monolayer ${\mathrm{Fe}}_{5}{\mathrm{GeTe}}_{2}$. We show that the nearest-neighbor approximation, often used in the literature, fails to describe the DMI. The strong DMI together with moderate in-plane magnetocrystalline anisotropy energy allows to stabilize nanoscale skyrmions in out-of-plane magnetic fields above $\ensuremath{\approx}2$ T. The energy barriers of skyrmions in monolayer ${\mathrm{Fe}}_{5}{\mathrm{GeTe}}_{2}$ are comparable to those of state-of-the-art transition-metal ultrathin films. We further predict that these nanoscale skyrmions can be stable for hours at temperatures up to 20 K.