Yong-Feng Li

Origin of ferromagnetism in Cu-doped SnO2: A first-principles study

We investigate the magnetic properties of Cu-doped SnO2, which was reported recently in experiments to possess ferromagnetism at room temperature, by first-principles calculations. Our results show that the doped system prefers the antiferromagnetic state for only Cu substitution. The oxygen vacancies are more inclined to form on the sites nearest to Cu defects. However, only those oxygen vacancies away from Cu defects contribute to the ferromagnetism significantly. Our results reveal that Sn vacancies are much easier to form than oxygen vacancies for their much lower formation energy. Moreover, the Cu-doped system always prefers the ferromagnetic state in the presence of Sn vacancies. Therefore, the origin of ferromagnetism in Cu-doped SnO2 can be attributed to the magnetic mediation of Sn vacancies.

Ferromagnetism of Cd doped SnO2: A first-principles study

The magnetic properties of Cd-doped SnO2 are studied by first-principles calculations. Our results reveal that the doped system favors a ferromagnetic state and high Curie-temperature can be expected in it. The doped Cd atoms do not tend to form clusters in tin oxide. The systems can be favorably synthesized in oxygen-rich ambient. The origin of ferromagnetism can be attributed to the hole-mediated p-d hybridization between Cd and O atoms.

Density-functional study on the ferromagnetism of Mn-doped SnO2

So far, both room-temperature ferromagnetism and paramagnetism have been reported in Mn-doped SnO2 films and their magnetic properties remain still puzzling. We have systematically investigated the magnetic properties of Mn-doped SnO2 by first-principles calculations. Our results reveal that the magnetic coupling is too weak and consequently paramagnetism is only found in the doped system when Mn substitutes Sn atoms. The formation energy of Mn impurity is much higher without the presence of vacancy, which prevents their substitutions significantly. In the presence of vacancies, the formation energy of Mn is greatly reduced and they can substitute Sn heavily. Compared to Sn vacancies, oxygen vacancies mediate the ferromagnetism much more effectively. The origin of ferromagnetism in Mn-doped SnO2 can be attributed to the oxygen-vacancy mediated RKKY interaction.