Strain effect on Magneto-crystalline anisotropy of atomically thin Fe₃GeTe₂

Two-dimensional magnetism [1, 2] has attracted huge attentions, where Fe₃GeTe₂ (FGT) has Curie temperature larger than 130 K [3]. Here, magneto-crystalline anisotropy (MCA) of mono- and bilayer FGT are studied with density functional theory. Perpendicular MCA, the preference for perpendicular magnetism, is advantageous for high bit density, thermal stability, and lower switching current [4]. Under strain (–5%≤η≤+5%), E_MCA of monolayer FGT varies from 0.85 to 4.15 meV/f.u.; that of bilayer FGT does from –0.56 to 4.82 meV/f.u. For both cases, under compressive (tensile) strain E_MCA decrease (changes little). From band analysis, without strain, (m=±1|L_Z|m=±1) contributes to E_MCA > 0. However, when η=–5%, due to upward band shift, m=±1 states become unoccupied: (m=0|L_X|m=±1) emerges giving E_MCA < 0. For monolayer, E_MCA > 0 contribution wins E_MCA < 0 for all η. On the other hand, for bilayer, E_MCA > 0 contribution wins E_MCA < 0 for all η except η≤–4%.

[1] Kenneth S. Burch et al., Nature 563, 47 (2018).

[2] M. Gibertini et al., Nat. Nanotechnol. 14, 408 (2019).

[3] Zaiyao Fei et al., Nat. Mater. 17, 778 (2018).

[4] Soon-Wook Jung et al., Appl. Phys. Lett. 92, 202508 (2008).