Theoretical study of magnetic ordering and electronic properties of AgxAl1−x N compounds

Ferromagnetic ordering of silver impurities in the AlN semiconductor is predicted by plane-wave ultrasoft pseudopotential and spin-polarized calculations based on density functional theory (DFT). It was found that an Ag impurity atom led to a ferromagnetic ground state in Ag0.0625Al0.9375N, with a net magnetic moment of 1.95 μBμB per supercell. The nitrogen neighbors at the basal plane in the AgN4 tetrahedron are found to be the main contributors to the magnetization. This magnetic behavior is different from the ones previously reported on transition metal (TM) based dilute magnetic semiconductor (DMS), where the magnetic moment of the TM atom impurity is higher than those of the anions bonded to it. The calculated electronic structure band reveals that the Ag-doped AlN is pp-type ferromagnetic semiconductor with a spin-polarized impurity band in the AlN band gap. In addition, the calculated density of states reveals that the ferromagnetic ground state originates from the strong hybridization between 4dd-Ag and 2pp-N states. This study shows that 4dd transition metals such as silver may also be considered as candidates for ferromagnetic dopants in semiconductors.

► Ag-doped AlN is a pp-type semiconductor.
► Silver can exhibit ferromagnetic order in the AlN host semiconductor.
► FM state originates from the strong hybridization between 4dd-Ag and 2pp-N states.
► The magnetic behavior is different from the ones reported on TM based DMS.