Figure 4.

The schematic view of the ferromagnetic coupling and anti-ferromagnetic coupling between the two Cr atoms doped in ZnO nanowires. The 3dlevels are showed and the energy levels include thep–dinteraction. The line with thedouble-headed arrowindicates that the two states with the same spin channel couple with each other

Shi and Duan Nanoscale Research Letters 2009 4:480-484   doi:10.1007/s11671-009-9260-7