Electron-spin-resonance Study of Polycrystalline Fe-doped ZnO Ceramics

The influence of Fe doping on the structural and the magnetic properties of polycrystalline ceramics of Zn1-x Fe (x) O (x = 0.01-0.30) was systematically investigated by means of X-ray diffraction (XRD), electron spin resonance (ESR), and a superconducting quantum interference device (SQUID) magnetometer. XRD patterns reveal the coexistence of two structural phases, wurtzite ZnO and spinel ZnFe2O4, even at x = 0.01. Both XRD and ESR data indicate that Fe ions are incorporated into the Zn sites of the ZnO host lattice and act as paramagnetic centers. The ESR spectral linewidth increases with increasing Fe concentration until x = 0.04 and then slightly decreases for x > 0.04. Compared with the variation tendency in the lattice parameters, we believe the Fe dopants in Zn1-x Fe (x) O to be Fe2+ and Fe3+ ions, where Fe3+ dominates in the compounds with x a parts per thousand currency sign 0.08 while Fe2+ dominates in the compounds with higher Fe concentrations. Exchange interactions due to Fe3+-Fe3+, Fe3+-Fe2+, and Fe2+-Fe2+ pairs are responsible for the ESR signals and the paramagnetic behavior of the samples.