High-Temperature Ferromagnetism in a Two-Dimensional Semiconductor with a Rectangular Spin Lattice

Abstract

Atomically thin two-dimensional (2D) ferromagnetic (FM) semiconductors with a high Curie temperature (TC) are essential and highly desired for nanoscale spintronic devices. However, the recently discovered 2D FM semiconductors show rather low TC (≤45 K), which limits their practical application. An important reason for the low TC is the lack of effective spin interactions. Here, we reveal that increasing the number of effective spin interactions by constructing a rectangular spin–lattice can significantly improve the TC of FM semiconductors. Based on this mechanism, we design a rectangular lattice of the CrO2 monolayer (denoted as R-CrO2) by performing global structural optimizations. The first-principles calculations show that the R-CrO2 is energetically more stable than the previously reported H- and T-CrO2. As expected, the R-CrO2 monolayer is an intrinsic FM semiconductor with TC up to ∼370 K, which is more than twice that of the T-CrO2 monolayer (∼150 K). This is because the R-CrO2 monolayer possesses four effective spin interactions between adjacent Cr sites, more than that of the T-CrO2 monolayer (3). These findings give rise to a new and efficient design principle for realizing high-temperature 2D FM semiconductors.