A Symmetry-Breaking Phase in Two-Dimensional FeTe₂ with Ferromagnetism above Room Temperature

Abstract

Recently, ferromagnetism observed in monolayer two-dimensional (2D) materials has attracted attention due to the promise of its application in next-generation spintronics. Here, we predict a symmetry-breaking phase in 2D FeTe2 that differs from conventional transition metal ditellurides shows superior stability and room-temperature ferromagnetism. Through density functional theory calculations, we find the exchange interactions in FeTe2 consist of short-range superexchange and long-range oscillatory exchanges mediated by itinerant electrons. For six nearest neighbors, the exchange constants are calculated to be 50.95, 33.41, 2.70, 11.02, 14.46, and −4.12 meV. Furthermore, the strong relativistic effects on Te2+ induce giant out-of-plane exchange anisotropy and open up a significantly large spin wave gap (ΔSW) of 1.22 meV. All of this leads to robust ferromagnetism with the T c surpassing 423 K, which is predicted by the renormalization group Monte Carlo method, sufficiently higher than room temperature. Our findings shed light on the promising future of FeTe2 in 2D magnetic research and spintronic applications.

FeSi2: a two-dimensional ferromagnet containing planar hexacoordinate Fe atoms

“…31,32 The Monte Carlo steps were set to 1.2 Â 10 5 on a 32 Â 32 lattice, and all of the renormalization group Monte Carlo algorithms described here were implemented in the MCSOLVER. 33 The solid-state adaptive natural density partitioning (SSAdNDP) algorithm was used to analyze the chemical bonding pattern of the FeSi 2 monolayer. 34 SSAdNDP is an extension of the AdNDP method in a periodic system and follows the concept of the periodic natural bond orbital method to interpret chemical bonding in terms of classical lone pairs, two-center bonds, and multi-center delocalized bonds.…”

Fe‐ and Co‐Doped Tungsten Disulfide Monolayers: 2D Ferromagnetic Half‐Metals at Room Temperature

“…All of the renormalization group Monte Carlo algorithms described here were implemented in open source project MCSOLVER. [ 36 ]…”

Large Vertical Piezoelectricity in a Janus Cr2I3F3 Monolayer

“…The phonon dispersions were performed utilizing a finite difference approach, as implemented in the Phonopy package, in which a 4 × 4 × 1 supercell is employed [30,31]. The Curie temperature (T C ) is evaluated by using the Metropolis Monte Carlo (MC) simulations implemented in mcsolver code [32,33].…”

“…The MAE (in unit of meV), the nearest neighbor (NN) exchange interaction J 1 , the next nearest neighbor (NNN) interaction J 2 , the third nearest neighbour (3NN) interaction J 3 (in unit of meV), and the Curie temperature T C (in unit of K) of the Cr 2 I 3 F 3 , CrF 3 , and CrI 3 monolayer. The Curie temperature (T C ) of the Cr 2 I 3 F 3 monolayer was evaluated by using the Metropolis Monte Carlo (MC) simulations implemented in mcsolver code [32,33]. To perform the evaluation, the exchange coupling J ex , consisting of the nearest neighbor (NN) exchange interaction J 1 , the next nearest neighbor (NNN) interaction J 2 , and the third nearest neighbour (3NN) interaction J 3 , is firstly calculated by combining DFT calculations with the Heisenberg spin Hamiltonian [7].…”