Decoupled strain response of ferroic properties in a multiferroic VOCl2 monolayer

Magnetoelectric Multiferroic Janus Monolayers VOXY (X/Y = F, Cl, Br, or I, and X ≠ Y) with In-Plane Ferroelectricity and Out-of-Plane Piezoelectricity

“…Note that the V ion polar displacement is directly correlated to the in-plane ferroelectric polarization in the VOXY monolayers, and thus an increase (decrease) in polar displacement results in an increase (decrease) in ferroelectric in-plane polarization. Similar results have also been observed for VOF 2 monolayer and for VOCl 2 monolayer, where VOF 2 shows a similar phase transition from FM to an AFM magnetic ordering on applying compressive strain and VOCl 2 shows a transition from AFM3 to FM ordering on applying tensile strain, with increase in ferroelectric polarization with tensile strain along the polar axis for both VOCl 2 and VOF 2 monolayers.…”

“…The difference in vanadium–oxygen bond lengths (V–O1 and V–O2) in each VOXY monolayer provides the polar displacement of the V ion along the in-plane polar axis ( a -axis), shown in Table S1. The V ion polar displacement is responsible for in-plane ferroelectricity in these systems, similar to their parent VOX 2 monolayers . The X–V–X bond angle is larger than the Y–V–Y bond angle due to higher repulsion among halogen atoms with higher electronegativity.…”

“…Though the first-ever experimental realization of a 2D multiferroic has been confirmed recently in 2022 only for monolayer NiI 2 , several 2D multiferroics have been discovered in the past decade using density functional theory (DFT) based theoretical methods. ,− Most of them have been identified as type-I multiferroics with very few type-II 2D multiferroics. , Recently, several studies have discovered and investigated a new family of 2D type-I multiferroics, VOX 2 (X = F, Cl, Br, or I). − VOX 2 monolayers show in-plane ferroelectricity while violating the d 0 rule since distortion of the V ion with partially occupied d 1 electronic configuration is responsible for ferroelectricity. Among the four members, VOF 2 and VOI 2 have been predicted to have ferromagnetic (FM) ground state spin ordering. , Later studies predict noncollinear spin texture as the ground state for the VOI 2 polar structure because the strong spin–orbit coupling (SOC) of the heavy element iodine leads to large Dzyaloshinki–Moriya interaction (DMI). , …”

Monolayer CrTe: a room temperature ferromagnetic half-metal

“…These include electronics [1][2][3][4] , energy storage 5 , transport 4,6,7 , optoelectronics [8][9][10] , sensors [11][12][13][14][15] , catalysis [16][17][18][19] and magnetism [20][21][22][23][24][25] . Among 2D materials 20,21,[25][26][27][28][29][30][31][32][33][34][35] , 2D magnets are highly desirable for use in modern spintronics and data storage devices. In non-magnetic 2D materials, extrinsic magnetic ordering can be induced via doping [36][37][38][39] , defect engineering 40,41 , proximity effect 42,43 , or strain engineering 44 .…”

Intrinsic ferromagnetism and the quantum anomalous Hall effect in two-dimensional MnOCl2 monolayers

“…Currently, 2D MOX 2 (M: transition metal; X: F, Cl, Br, and I) monolayers have been well studied because of their intrinsic excellent physical properties. 14–16 Ferroelectric (FE) distortion occurs along the a -axis as a result of strong electron–phonon interactions, which not only allow ferroelectricity and ferromagnetism to coexist in the VOX 2 monolayer, 17–21 but also enable electric-field switching of magnetic topological charge through the mediation of coupled polarization and Dzyaloshinskii–Moriya interactions. 22 Furthermore, NbOI 2 has been found to have a spin texture controlled by ferroelectric switching, 23 peculiar optical properties, 24,25 and the highest in-plane piezoelectric stress coefficient among 2D materials, allowing for highly efficient electrical–mechanical energy conversion.…”