Sustained ferromagnetism induced by H-vacancies in graphane.

The electronic and magnetic properties of graphane flakes with H-vacancies were investigated using quantum-chemistry methods. The hybridization of the edges is found to be absolutely crucial in defining the size of the HOMO-LUMO gap, which is increased from 3.04 to 7.51 eV when the hybridization is changed from the sp(2) to the sp(3) type. The H-vacancy defects also influence the size of the gap, which depends on the number of defects and their distribution between the two sides of the graphane plane. Further, the H-vacancy defects induced on one side of the graphane plane and placed on the neighboring carbon atoms are found to be the source of ferromagnetism which is distinguished by the high stability of the state with a large spin number in comparison to that of the singlet state and is expected to persist even at room temperatures. However, the ferromagnetic ordering of the spins is found to be limited by the concentration of H-vacancy defects and ordering would be preserved if number of defects does not exceed eight.