Hualong Tao

EFFECTS OF OXYGEN VACANCY ON MAGNETIC PROPERTIES OF COBALT-DOPED ZnO DILUTE MAGNETIC SEMICONDUCTORS

Effects of oxygen vacancy (Vo) on magnetic properties of Co-doped ZnO are investigated by first principle calculations. The calculated formation energies of Vo with different bonding to Co atom indicate that Vo prefers location near Co atom, implying a strong local interaction between the Co atom and O-vacancy. Induced by Vo, the Co-3d and O-2p valence bands upward shift towards the Fermi level, leading to the presence of additional carriers at the Fermi level. The delocalized carriers and the substitutional Co ion play a key role in the occurrence and stability of ferromagnetism of Co-doped ZnO.

First-principles study on ferromagnetism in 4H-SiC codoped with Al and Mn

The electronic structures and magnetic properties in 4H-SiC codoped with Al and Mn have been investigated systematically based on density functional theory. Our results show that (Al,Mn)-codoping introduces spin-polarized hole states in 4H-SiC. The codoped system prefers the ferromagnetic state and the magnetization energy is larger than some of the known room-temperature diluted magnetic semiconductors (DMSs), indicating high RT ferromagnetism for (Al,Mn): 4H-SiC can be expected. The ferromagnetic property is mainly attributed to the 3d orbitals of Mn. Besides that the coupling of Mn–C–Mn also plays important roles in enhancing ferromagnetism in the case with more than one Mn atom. Our study explains the intrinsic factors inducing magnetism in 4H-SiC, which may provide a promising approach for preparing DMSs.