Oxygen vacancy induced ferromagnetism in ball milled Zn0.97Ni0.03O: Confirmation through electron spin resonance

Abstract

Among the semiconducting materials, ZnO is a versatile multifunctional candidate with a direct band gap of 3.37 eV at 300 K and large excitonic binding energy of 60 meV which can be useful for spintronics device applications. ZnO has high solubility for transition metals. The transition metals which have been used for DMS, Ni is the most efficient doping element to improve the electrical, magnetic properties of ZnO. Ni doped ZnO would be a good candidate to achieve ferromagnetic property with a high curie temperature i.e. above the room temperature. In this study, Zn1−xNixO (x = 0.03) powder sample was successfully synthesized by a ball milling technique. The X-ray diffraction analysis confirms the polycrystalline, hexagonal wurzite structure for 3% Ni doped ZnO nanoparticles. The substitution of Ni in the ZnO matrix has been confirmed by micro-Raman analysis with the observation of E2 (High) vibrational mode at 437 cm−1 which refers to the strongest mode of vibration in wurtzite crystal structure. A broadened peak observed at 570 cm−1 informs about the presence of clusters of oxygen vacancies. VSM measurement of the sample shows the ferromagnetic hysteresis loop at room temperature with saturation moment of 9 × 10−5 emu/g. The calculated ‘g’ value of 1.95 from electron spin resonance spectrum suggests that the observed ferromagnetism is due to the oxygen vacancy.