Critical analysis of the vacancy induced magnetism in Scandium Nitride (ScN): An ab-initio study

• ScN with cation vacancy leads to a non-vanishing total magnetic moment.
• The spin polarization energy is well above temperature energy.
• The magnetic state cannot be enhanced by strain.
• The magnetic percolation can be achieved by applying an external strain.

We have studied the origin of the magnetism induced by a neutral cation vacancy in rocksalt ScN using ab-initio   calculations based on spin density functional theory. Our results showed that Sc vacancy induces a total local magnetic moment of 0.50μB0.50μB. The main contributors to this induced magnetism are the 2p2p orbitals of nearest nitrogen atoms surrounding the vacancy. The spin polarization energy (defined as the energy difference between the spin polarized and non-polarized states) is well above the room-temperature energy. Furthermore, we have investigated the effect of an external strain on the induced magnetism. Our calculations showed that applying an external strain leads to a decrease of the stability of the magnetic state. Moreover, calculations of the magnetic interactions showed that the most stable configuration corresponds to the fifth nearest neighbor distance with a ferromagnetic state. Finally, using thermodynamic considerations, we demonstrated that the minimum defect concentration to achieve magnetic percolation cannot be reached at equilibrium conditions. However, we found that by applying an external strain, we could reduce the formation energy of the defect, achieving therefore the magnetic percolation.