We report on magnetic and structural properties of n- and p-type GaN layers implanted with Mn, Cr, and V. The samples were subsequently annealed in a N(2) atmosphere at a constant temperature in the range between 700 and 1050degreesC. Measurements of the magnetization as a function of magnetic field as well as of the temperature show typical paramagnetic behavior. In addition, a weak antiferromagnetic coupling between the implanted ions was observed. 3d-metal rich precipitates of crystalline nature are revealed by high resolution transmission electron microscopy. (C) 2004 American Institute of Physics.