Two-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>5</mml:mn><mml:mi>d</mml:mi></mml:mrow></mml:math> multiferroic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">W</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Cl</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:mrow></mml:math>: Breathing kagome lattice and tunable magneto-optical Kerr effect
Di Hu, Haoshen Ye, Ning Ding, Kaidi Xu, Shan‐Shan Wang, Shuai Dong, Xiaoyan Yao
Abstract
Owing to the strong spin-orbit coupling and the related fascinating physical properties, heavy $5d$ transition metals exhibit desirable application prospects. However, up to now, the $5d$ magnetic materials are still very limited, especially very rare for tungsten. In this work, we theoretically predict a two-dimensional multiferroic ${\mathrm{W}}_{3}{\mathrm{Cl}}_{8}$ monolayer. Intrinsic $5d$ magnetism of tungsten is activated by the W ions' fractional valence in a breathing kagome lattice of reduced effective dimension. A coplanar $Y$-type antiferromagnetism composed by ferromagnetic ${\mathrm{W}}_{3}$ trimers is confirmed as the magnetic ground state. The spontaneous ferroelectric polarization mainly originates from the ion displacement induced by the breathing distortion of kagome lattice. An intrinsic magneto-optical Kerr effect with sizable Kerr angle can be observed to detect this trimeric $Y$-type antiferromagnetism, and it depends strongly on the detailed magnetic order. Thereby, we propose a general scheme for realizing more $5d$ magnetism in two-dimensional multiferroic systems.