Abstract
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.
Highlights
We report on the magnetic properties of GaN:Gd layers grown by molecular beam epitaxy
The aim is to introduce magnetic impurities that provide local spins in a nonmagnetic host and to have a long-range interaction mechanism between them that can lead to ferromagnetism at or above room temperature
The first report on ferromagnetic GaN:Gd was on a molecular beam epitaxy (MBE)-grown layer with ∼6% of Gd
Summary
We report on the magnetic properties of GaN:Gd layers grown by molecular beam epitaxy. Of magnitude as compared to unintentionally doped GaN.20 The observed variable-range hopping in an impurity band of localized states is another hint that deep defects form in a large number, even for low Gd concentrations.
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