Effects of Copper Dopants on the Magnetic Property of Lightly Cu-Doped ZnO Nanocrystals

Abstract

To explore the origin of magnetism, the effect of light Cu-doping on ferromagnetic and photoluminescence properties of ZnO nanocrystals was investigated. These Cu-doped ZnO nanocrystals were prepared using a facile solution method. The Cu2+ and Cu+ ions were incorporated into Zn sites, as revealed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). At the Cu concentration of 0.25 at.%, the saturated magnetization reached the maximum and then decreased with increasing Cu concentration. With increasing Cu concentration, the photoluminescence (PL) spectroscopy indicated the distribution of VO+ and VO++ vacancies nearly unchanged. These results indicate that Cu ions can enhance the long-range ferromagnetic ordering at an ultralow concentration, but antiferromagnetic “Cu+-Vo-Cu2+” couples may also be generated, even at a very low Cu-doping concentration.

Experimental and ab initio studies on the structural, magnetic, photocatalytic, and antibacterial properties of Cu-doped ZnO nanoparticles

“…19 Wang et al have experimentally shown that the Cu ions can enhance the long-range ferromagnetic ordering at an ultralow concentration via the indirect double exchange mechanism, but antiferromagnetic "Cu + -V 0 -Cu 2+ " coupling may also be generated, as a superexchange mechanism, even at a very low Cu-doping concentration. 20 One of the key objectives of this work was to determine quantitively the amount of Cu inserted into the ZnO host matrix. Some researchers have noticed that the hexacoordinated ionic radius of Cu 2+ (0.73 Å) is slightly smaller than the one of Zn 2+ (0.74 Å), they have argued that this could solve the determination of the copper content by scrutinizing its effect on the lattice parameters that should decrease upon doping with Cu.…”

“…19 Wang et al have experimentally shown that the Cu ions can enhance the long-range ferromagnetic ordering at an ultralow concentration via the indirect double exchange mechanism, but antiferromagnetic “Cu + –V 0 –Cu 2+ ” coupling may also be generated, as a super-exchange mechanism, even at a very low Cu-doping concentration. 20…”