Magnetic properties of sol-gel-derived doped ZnO as a potential ferromagnetic semiconductor: a synchrotron-based study

A variety of x-ray techniques is employed to investigate sol-gel-synthesized Co- and Mn-doped ZnO films. X-ray diffraction (XRD) shows that the dominant structure is the c-axis orientated wurtzite ZnO. Dopant K-edge extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) indicate that the Co and Mn ions are fourfold co-ordinated with valency 2+/3+ and 3+/4+, respectively. Surface-sensitive dopant L-edge XANES and x-ray magnetic circular dichroism (XMCD) for the Co dopant are well described by atomic multiplet calculations for tetrahedral Co2+, while for Mn the data indicate that the symmetry is lowered due to Jahn-Teller distortion. The XMCD show conclusively that both Co- and Mn-doped ZnO films are purely paramagnetic.