Strain-tunable Dzyaloshinskii-Moriya interaction and skyrmions in two-dimensional Janus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Cr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>X</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Y</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>X</mml:mi><mml:mo>,</mml:mo><mml:mo> </mml:mo><mml:mi>Y</mml:mi></mml:math> = Cl, Br, I, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>X</mml:mi><mml:mo>≠</mml:mo><mml:mi>Y</mml:mi></mml:mrow></mml:math>) trihalide monolayers
Zhong Shen, Changsheng Song, Yufei Xue, Zebin Wu, Jiqing Wang, Zhicheng Zhong
Abstract
Recently, great effort has been devoted to the search for two-dimensional (2D) ferromagnetic materials with inherent strong Dzyaloshinskii-Moriya interaction (DMI). Here, through a first-principles approach, we systematically investigate the effect of biaxial strain on the DMI, the Heisenberg exchange interaction, and the magnetic anisotropy energy (MAE) of Janus ${\mathrm{Cr}}_{2}{X}_{3}{Y}_{3}$ ($X,Y$ = Cl, Br, I, $X\ensuremath{\ne}Y$) monolayers. Both DMI and MAE can be significantly enhanced by tensile strain, whereas a reversal of the chirality of DMI in ${\mathrm{Cr}}_{2}{\mathrm{Cl}}_{3}{\mathrm{Br}}_{3}$ and a switch of MAE from off plane to in plane in ${\mathrm{Cr}}_{2}{\mathrm{I}}_{3}{\mathrm{Cl}}_{3}$ are induced by a compressive strain of $2%$. Microscopically, DMI and MAE are associated mainly with the large spin-orbit coupling of the heavy nonmagnetic halogen atoms rather than that of the magnetic Cr atoms. In particular, the peculiar magnetic transition of ${\mathrm{Cr}}_{2}{\mathrm{I}}_{3}{\mathrm{Cl}}_{3}$ is explained by competition between direct exchange and superexchange interactions. Micromagnetic simulations show that a small external magnetic field of 65 mT stabilizes a skyrmion with a diameter of 9.8 nm in the ${\mathrm{Cr}}_{2}{\mathrm{I}}_{3}{\mathrm{Cl}}_{3}$ monolayer. Our results will provide guidance for further research on DMI and skyrmions in 2D Janus materials as well as a basis for the potential applications in spintronic devices.