Strain-Induced Magnetism in Defective Graphene

Vacancy defects are known to induce magnetization in graphene. However, understanding the effects of defect-defect interaction on magnetization under applied strain remains elusive. This talk will present the effects of symmetry-breaking strain on magnetization in multidefect graphene. We used the density functional theory simulation under the generalized gradient approximation for the exchange-correlation energy to investigate the magnetic consequence of strain applied along different directions relative to the defect pair. Our results show that the spin magnetic moment increases with increasing strain. Decomposition of the total magnetic effects into the individual effects of the orbitals reveals that the $p_z$ orbital dominates the change in the total magnetic moment, while the net change of the local moment in $p_x$ and $p_y$ orbitals are the same but with opposite signs. Nonetheless, for a pair of monovacancies, the strain does not affect the spin magnetic moment when the inter-defect distance reaches a critical value. However, the magnetic moment increases with increasing strain for a longer inter-defect distance, and the combined effects can be well-approximated as a linear superposition of their individual effects. Additionally, if the defects are magnetically isolated, there exists a critical strain whereat each of the defects experiences a second-order Jahn–Teller reconstruction (JTRR) that switches the orientation of the defect and alters the magnitude of the magnetic moment. These results are expected to shed new light on controlling the magnetic behavior of a single or multi-defect system as a function of the separation distance and the intensity of mechanical strain.