However, simultaneous pressure- and temperature-dependent lattice vibrations and spin–phonon interactions have not been reported experimentally. Previous studies have reported an anomalous pressure-induced phonon softening behavior and a temperature-driven strong spin–phonon coupling in FGT through Raman studies. Raman spectroscopy is a powerful technique for probing the lattice vibrations in a crystal. Though, there is a lack of study on how strong/weak the spin–phonon coupling is for each of the modes. The first-principles calculations reported an increase of the frequencies of the and E 2g Raman modes when the spin ordering in FGT changes from FM to AFM, indicating notable spin–phonon coupling for these Raman modes in FGT. The Fe I and Fe II atoms in each layer contribute to both the itinerant electrons and local ferromagnetic moments, which play significant roles in the magnetic spin-order transition with pressure and temperature dependence. The planar Fe IIGe is sandwiched by two planes of Fe I atoms, and the triple planes are then sandwiched by two layers of Te atoms. Each layer comprises five covalently bonded atomic planes. The unit cell has two layers that are bonded by interlayer van der Waals (vdW) interactions. įGT crystallizes in a hexagonal structure with space group P6 3/mmc (No. Fe 3GeTe 2 (FGT), a valuable member of 2D layered magnetic materials, has attracted special interests recently due to its rare metallic itinerant ferromagnetism with high Curie temperature (≈230 K) and novel physical properties, including anomalous hall effect, Kondo effect, and giant tunneling magnetoresistance. This breakthrough promotes tremendous effort in exploring the potential applications of 2D magnetic materials in magnetoelectrics, electrical control of magnetism, and magnetic tunnel junction. However, the discovery of long-range ferromagnetic order in Cr 2Ge 2Te 6 and CrI 3 monolayers breaks the conventional theorem. In two-dimensional (2D) materials, according to the conventional Mermin–Wagner theorem, thermal fluctuations could strongly suppress the magnetic order of materials. The intensive research on magnetic thin films has been driven by the rapid development of nanoelectronic and spintronic devices.
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