Mixtures of powders of manganese, silicon and metallic gallium were annealed in a stream of ammonia at 1000-1050 degrees C. The products obtained were bulk single crystals of gallium nitride, dimensions up to 4.8 x 1.0 x 0.1 mm. The concentrations of the dopants were: Mn 7.8 +/-0.12 at% and Si 0.5 +/- 0.2 at%. The influence of the process parameters (temperature, ammonia flow rate and composition of the Mn and Si mixtures in the substrate material) on the doping level of the obtained Ga(Mn,Si)N bulk single crystals was studied. Measurements involving X-ray diffraction and Raman methods confirmed good structural properties of Ga(Mn,Si)N single crystals. To characterize the magnetic properties of our materials, their magnetization was measured as a function of magnetic field. (c) 2006 Elsevier B.V. All rights reserved.