Spin-Strain Phase Diagram of Defective Graphene

Abstract: Using calculations on defective graphene from first principles, we herein consider the dependence of the properties of the monovacancy of graphene under isotropic strain, with a particular focus on spin moments. At zero strain, the vacancy shows a spin moment of 1.5 $\mu_B$ that increases to $\sim$2 $\mu_B$ when the graphene is in tension. The changes are more dramatic under compression, in that the vacancy becomes non-magnetic when graphene is compressed more than 2%. This transition is linked to changes in the atomic structure that occurs around vacancies, and is associated with the formation of ripples. For compressions slightly greater than 3%, this rippling leads to the formation of a heavily reconstructed vacancy structure that consists of two deformed hexagons and pentagons. Our results suggest that any defect-induced magnetism that occurs in graphene can be controlled by applying a strain, or some other mechanical deformations.