Superparamagnetic nanoparticles formed in Fe-implanted ZnO

Due to its potential application to diluted magnetic oxides, transition metal doped ZnO has been under intensive investigation. We present a correlation between the structural and the magnetic properties of Fe implanted ZnO bulk crystals. Crystalline damage recovery, structural and magnetic properties are studied by Rutherford backscattering spectrometry and channelling (RBS/C), synchrotron radiation X-ray diffraction (SR-XRD), and superconducting quantum interference device magnetometer (SQUID), respectively. The 623 K Fe ion implantation and the high vacuum annealing at 823 K lead to the formation of secondary phase -Fe and -Fe nanoparticles. The discrepancy between the zero-field cooling and the field cooling curves further indicates that Fe-implanted ZnO is superparamagnetic and the observed ferromagnetism originates from the Fe nanoparticles.