Zeeman Splitting-Induced Positive Magnetoresistance in Co-Doped ZnO and Co-Doped Cu $_{2}$ O Ferromagnetic Nanoparticles

Magnetoresistance of cobalt-doped zinc oxide and cuprous oxide ferromagnetic nanoparticles with different cobalt concentrations are studied. Zeeman splitting effect is found to play a key role in the electrical transport of our cobalt-doped oxide ferromagnetic nanoparticles. We emphasize that the existence of large Zeeman splitting effect can be used in spintronics devices, because a very large and linear positive magnetoresistance (PMR) up to 780% is observed in the low field for the Co-doped ZnO. Small PMR in Co-doped Cu₂O relates to its small p-d exchange interaction. Codoping with other transition metals in Cu₂O is suggested to improve the ferromagnetism and magnetoresistance.