Insight into strain and electronic correlation dependent magnetism in monolayer 1T−CrTe2

$1T$-phase $\mathrm{Cr}{\mathrm{Te}}_{2}$ $(1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2})$ has received considerable interest recently due to its high Curie temperature $({T}_{C})$, which is desirable for practical spintronics applications. However, various magnetic behaviors of $1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2}$ have been reported in recent experimental and theoretical studies when its thickness reduces to ultrathin limit. In this work, the magnetic diagram of monolayer (ML) $1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2}$ with respect to in-plane biaxial strain and on-site Coulomb repulsion $U$ is obtained based on first-principles calculations. Our results indicate that the magnetic order of ML $1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2}$ can vary among ferromagnets and antiferromagnets with strain and electronic correlation. We show that the large exchange anisotropy and higher-order biquadratic interactions are crucial to accurately describe the spin energies in ML $1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2}$. The perplexing dependencies of the magnetocrystalline anisotropy on strain and $U$ are then well explained. Our work not only gives insight into the fundamental understanding of the unusual magnetic properties of ML $1T\text{\ensuremath{-}}\mathrm{Cr}{\mathrm{Te}}_{2}$, which is helpful to understand the diverse observations on the magnetic order in $\mathrm{Cr}{\mathrm{Te}}_{2}$, but also sheds light on engineering their performance for spintronic devices.