Quenching of ferromagnetism in bulk ZnO upon Mn doping

We shall present here some experimental results showing quenching of ferromagnetism in bulk ZnO upon Mn doping. We observed magnetic hysteresis for undoped bulk ZnO samples and the hysteresis is observed at room temperature and below. For the undoped bulk ZnO sample, the zero field cooled (ZFC) and field cooled (FC) bifurcation is observed above room temperature and this bifurcation can be associated due to ferromagnetism because below this temperature the sample show hysteresis and this temperature is associated to ferromagnetic Curie transition temperature Tc. The ferromagnetic transition temperature Tc above room temperature gets quenched upon doping ZnO samples with Mn. We shall try to understand what is the role of transition metal as dopant (such as Mn) in bulk wide band gap semiconductor and nonmagnetic metal oxide such as ZnO in its magnetic property.