VZn–H complex defect induced ferromagnetic behavior of unintentional hydrogen doped ZnO nanoparticles

Abstract

We explored the presence of uncanny ferromagnetic-like nature from unintentional hydrogen doped ZnO nanoparticles (NPs) using the combined results of SQUID, EPR, and NMR spectroscopy. The SQUID magnetometer reveals an apparent magnetization, coexistence of ferromagnetic and anti-ferromagnetic nature, negative-magnetization, and disordered magnetic behavior of ZnO NPs. This type of unusual ferromagnetic-like nature observed from non-magnetic ZnO NPs is encouraged due to the existence of undoubtedly native-defects such as zinc-vacancy (VZn), vacancy clusters, and donor-vacancy associated complexes (H–VZn), which are induced either by doping of magnetic or non-magnetic impurities. Further, the electron or hole trapped by complex-defects and polaronic states induces the ferromagnetic-like characteristics in the nano-scale ZnO. Photo-EPR and NMR studies confirm that the presence of hydrogen at the lattice position and in the vicinity of defective ZnO NPs bound with VZn form the donor-vacancy complex-defects. This nano-scale ZnO may be tunable for the applications of the magneto-optic and magnetostriction effect.