In order to elucidate the nature of ferromagnetic signatures observed in (Zn,Co)O we have examined experimentally and theoretically magnetic properties and spin-dependent quantum localization effects that control low-temperature magnetoresistance. Our findings, together with a through structural characterization, substantiate the model assigning spontaneous magnetization of (Zn,Co)O to uncompensated spins at the surface of antiferromagnetic nanocrystal of Co-rich wurtzite (Zn,Co)O. The model explains a large anisotropy observed in both magnetization and magnetoresistance in terms of spin hamiltonian of Co ions in the crystal field of the wurtzite lattice.
@article{arxiv.0708.2476,
title = {Origin of ferromagnetism in (Zn,Co)O from magnetization and spin-dependent magnetoresistance},
author = {T. Dietl and T. Andrearczyk and A. Lipińska and M. Kiecana and Maureen Tay and Yihong Wu},
journal= {arXiv preprint arXiv:0708.2476},
year = {2008}
}