Tracking defect-induced ferromagnetism in GaN:Gd
  We report on the magnetic properties of GaN:Gd layers grown by molecular beam epitaxy (MBE). A poor reproducibility with respect to the magnetic properties is found in these samples. Our results show strong indications that defects with a concentration of the order of 10^19 cm^-3 might play an important role for the magnetic properties. Positron annihilation spectroscopy does not support the suggested connection between the ferromagnetism and the Ga vacancy in GaN:Gd. Oxygen co-doping of GaN:Gd promotes ferromagnetism at room temperature and points to a role of oxygen for mediating ferromagnetic interactions in Gd doped GaN. 
Martin Roever (1) and Joerg Malindretos (1) and Amilcar Bedoya-Pinto   (1) and Angela Rizzi (1) and Christian Rauch (2) and ...
cond-mat.mtrl-sci