We report on the observation of electron paramagnetic resonance of manganese and nickel trace impurities in bulk GaN crystals gown by the sublimation sandwich method. The resolved hyperfine structure due to interaction wioth ~(55)Mn (1 chemical bounds 5/2) nuclei has been observed in GaN, allowing nuambiguous identification of the impurity. Manganese and nickel exist in Mn~(2+) (3d~( delta ) and Ni~(3+) (3d~7) charge states with electron spin S chemical bounds 1.999, A chemical bounds 70.10~(-4) cm~(-1) and fine structure parameter |D| chemical bounds 240 centre dot 10~(-4) cm~(-4). The EPR spectrum of Ni~(3+) in GaN has the characteristic anisotropy of an S chemical bounds 3/2 system in a strong axial crystalline field. The effective g-factor values were found to be g||~/ chemical bounds 2.10 and perpendicular ~/ approx = 4.20 for a system with an effective spin S~/ chemical bounds 1/2. An analogy was revealed between the parameters of M~(2=) and Ni~(3+) in GaN and ZnO crystals. The zero-phonon line at 1.047 eV seems to belong to the transition ~4T_2(F)-~4A_2(F) within 3dlevels of Ni~(3+) ion with a 3d~7 electronic configuration.
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