The effect of nitrogen on the magnetic properties of C-doped ZnO has been investigated. It has been found that a low concentration of N doping does not lead to an apparent change of the magnetization in C-doped ZnO films. When N doping concentration exceeds 0.05 at. %, the magnetization of C–ZnO films increases significantly (more than 85%). The increased magnetization is mainly due to the enhanced moment of carbon, resulted from N doping. The successful fabrication of p-type diluted magnetic semiconductor may be of interest for spintronic applications.

The effects of N-induced acceptor defects on tuning optical, transport, and magnetic properties of In 2 O 3 films fabricated by magnetron sputtering technique were investigated systematically by X-ray diffraction, X-ray photoelectron spectroscopy, UV−visible absorbance, Hall effect, film resistivity (ρ) versus temperature, magnetoresistance, and magnetic measurements. Detailed structural analyses reveal that N-doped In 2 O 3 films have a cubic bixbyite structure with the substitutional N defect at the O sites of In 2 O 3 lattice. The N-doped In 2 O 3 films display clear room-temperature ferromagnetic behavior and Mott variable range-hopping transport behavior. With increasing N-doping concentration, the saturated magnetization of the films monotonically increases and the conductivity transforms into p-type. Crossover of negative to positive magnetoresistance and a red shift of the optical band gap E g are also observed with N-doping. First-principles calculations show that the localized holes induced by N-doping can mediate the magnetic interaction by short-range N 1 :p-In:d/p-N 2 :p hybridization in N-doped In 2 O 3 system. Therefore, the intrinsic ferromagnetic ordering in N-doped In 2 O 3 films can be attributed to p−p interaction between N 2p orbitals, which causes a large Zeeman-split effect to suppress the carrier's hopping path, leading to formation of positive magnetoresistance.

The effects of Co doping on the structural, optical, magnetic and transport properties of (InCoSn)O films grown by RF-magnetron sputtering were systematically investigated by theoretical and experimental techniques. The detailed structural analyses revealed that all the (InCoSn)O films possess the cubic bixbyite structure, with the substitutional Co at the In sites of the InO matrix, while some of the Co atoms form Co metal clusters. Obvious room-temperature (RT) ferromagnetic behavior was observed and the saturated magnetization (M) first increased, then decreased with increased Co concentration, while carrier concentration n decreased monotonically, implying that the Co metal clusters are superparamagnetic and the observed RT ferromagnetism is not mediated by the charge carriers. The Mott variable range hopping (VRH) and hard band gap hopping transport behavior dominates the conduction mechanism of the films, confirming that the carriers are strongly localized. The UV-Vis and photoluminescence (PL) measurements indicate the decreased optical band gap E with Co doping, and further prove that the oxygen vacancies and Co impurity band form defect complexes of donor-acceptor pairs. The density functional theoretical calculations show that the codoped Sn can change the magnetic coupling between two Co ions from antiferromagnetic to ferromagnetic by the new hybridization between the Co 3d states with the Sn induced donor band. It can be concluded that the bound magnetic polaron (BMP) based oxygen vacancies as well as the Co-O-Co ferromagnetic superexchange interaction induced by Sn codoping may be responsible for the intrinsic ferromagnetic ordering in the (InCoSn)O films. These results may provide new insight for understanding the magnetic mechanism of InO based DMS systems.

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