Contrasting magnetism in VPS3 and CrI3 monolayers with the common honeycomb S = 3/2 spin lattice

Abstract

Two-dimensional (2D) magnetic materials are promising candidates for spintronics and quantum technologies. One extensively studied example is the ferromagnetic (FM) CrI${}_3$ monolayer with the honeycomb Cr${}^{3+}$ ($t_{2g}^3$, $S$ = 3/2) spin lattice, while VPS${}_3$ has a same honeycomb $S$ = 3/2 spin lattice (V${}^{2+}$, $t_{2g}^3$) but displays N$\acute{e}$el antiferromagnetism (AFM). In this work, we study the electronic structure and particularly the contrasting magnetism of VPS${}_3$ and CrI${}_3$ monolayers. We find that VPS${}_3$ is a Mott-Hubbard insulator but CrI${}_3$ is a charge-transfer insulator, and therefore their magnetic exchange mechanisms are essentially different. The first nearest-neighbor (1NN) direct $d$-$d$ exchange dominates in VPS${}_3$, thus leading to a strong antiferromagnetic (AF) coupling. However, the formation of vanadium vacancies, associated with instability of the low-valence V${}^{2+}$ ions, suppresses the AF coupling and thus strongly reduces the N$\acute{e}$el temperature ($T_{\text{N}}$) in line with the experimental observation. In contrast, our results reveal that the major 1NN $d$-$p$-$d$ superexchanges in CrI${}_3$ via different channels give rise to competing FM and AF couplings, ultimately resulting in a weak FM coupling as observed experimentally. After revisiting several important superexchange channels reported in the literature, based on our MLWFs and tight-binding analyses, we note that some antiphase contributions must be subtly and simultaneously considered, and thus we provide a deeper insight into the FM coupling of CrI${}_3$. Moreover, we identify and compare the major contributions to the magnetic anisotropy, i.e., a weak shape anisotropy in VPS${}_3$ and a relatively strong exchange anisotropy in CrI${}_3$.

16 pages, 12 figures, 3 tables

References in corpus (5)

• Ising-Type Magnetic Ordering in Atomically Thin FePS3
• Linear magneto-electric phase in ultrathin MnPS${}_3$ probed by optical second harmonic generation
• The magnetic properties and structure of the quasi-two-dimensional antiferromagnet CoPS${}_3$
• Possible persistence of multiferroic order down to bilayer limit of van der Waals material NiI${}_2$
• Understanding the Ising zigzag antiferromagnetism of FePS3 and FePSe3 monolayers