Spin–Phonon Interactions and Anharmonic Lattice Dynamics in Fe3GeTe2

Abstract Raman scattering is performed on Fe3GeTe2 (FGT) at temperatures from 8 to 300 K and under pressures from the ambient pressure to 9.43 GPa. Temperature‐dependent and pressure‐dependent Raman spectra are reported. The results reveal respective anomalous softening and moderate stiffening of the two Raman active modes as a result of the increase of pressure. The anomalous softening suggests anharmonic phonon dynamics and strong spin–phonon coupling. Pressure‐dependent density functional theory and phonon calculations are conducted and used to study the magnetic properties of FGT and assign the observed Raman modes, E2g2$E_{2{ m{g}}}^2$ and A1g1$A_{1{ m{g}}}^1$. The calculations proved the strong spin–phonon coupling for the E2g2$E_{2{ m{g}}}^2$ mode. In addition, a synergistic interplay of pressure‐induced reduction of spin exchange interactions and spin–orbit coupling effect accounts for the softening of the E2g2$E_{2{ m{g}}}^2$ mode as pressure increases

Transformation of trigonal planar B4 into zigzag B4 units within the new boride series Ti2–xM1+x–δIr3+δB3 (x = 0.5 for M = V–Mn, x = 0 for M = Mn–Ni and δ < 0.2)

In metal-rich borides, numerous boron fragments B-n (n = 2, 3, 4, 5, 6) have been discovered, the B-4 units being the most versatile with four different shapes (bent, zigzag, trigonal planar and tetrahedral). We report on the new boride series Ti2-xM1+x-delta Ir3+delta B3 (x = 0.5 for M = V-Mn, x = 0 for M = Mn-Ni and delta < 0.2), in which a structural change occurs by successive substitution of the 3d transition metal M = V, Cr, Mn, Fe, Co and Ni. It is found that the change in structure from the Ti1+xOs2-xRuB2-type structure (P (6) over bar 2m, no. 189) to the Ti1+xRh2-x+yIr3-yB3-type (Pbam, no. 55) leads to a change of B-4 shape from trigonal planar B-4 (M = V-Mn) to zigzag B-4 fragment (M = Mn-Ni). Even though there is no group-subgroup relationship between the two structures, we present how the Ti1+xOs2-xRuB2-type structure can easily be geometrically derived from the Ti1+xRh2-x+yIr3-yB3-type.This article is published as Scheifers, Jan P., Michael Küpers, Yuemei Zhang, Laura Lutz‒Kappelman, Gordon J. Miller, and Boniface PT Fokwa. "Transformation of trigonal planar B4 into zigzag B4 units within the new boride series Ti2–xM1+ x–δIr3+ δB3 (x= 0.5 for M= V–Mn, x= 0 for M= Mn–Ni and δ< 0.2)." Solid State Sciences 107 (2020): 106294. DOI:10.1016/j.solidstatesciences.2020.106294. Copyright 2020 Published by Elsevier Masson SAS. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Posted with permission