Magnetic and structural properties of Gd-implanted zinc-blende GaN

Zinc-blende GaN layers grown by molecular beam epitaxy were uniformly focused-ion-beam implanted with 300keV Gd3+ ions for doses ranging from 1×1012to1×1015cm−2, and their structural and magnetic properties were studied. The implanted samples were not subjected to any annealing treatment. Only Gd incorporation into zinc-blende GaN was observed by x-ray diffraction. Magnetic investigations using superconducting quantum interference device magnetometry reveal a (super)paramagneticlike behavior with an ordering temperature around 60K for the sample with the highest implantation dose. Our experimental studies indicate that the spontaneous electric polarization in wurtzite GaN is the crucial mechanism for its ferromagneticlike behavior upon Gd doping.