The effects of Zn and Ga doping on the magnetic ordering of the Pr spins in PrBa2(Cu(1-x)M(x))(3)O-7, where M = Zn and Ga, were studied using neutron diffraction and ac susceptibility measurements. The Pr spins along the c-axis are found to change from nearest-neighbors being antiparallel for undoped systems to nearest-neighbors being parallel for both Zn-doped and Ga-doped systems, while the spin arrangement in the ab-plane remains unaltered. The spin reversal along the c-axis is more sensitive to the presence of Zn atoms than to that of Ga atoms. On the other hand, the ordering temperature of Pr decreases as the Ga concentration is increased but it is not affected by the presence of Zn atoms. Order-parameter measurements made for the undoped, Zn-doped, and Ga-doped compounds all give values that are close to 0.5 for the critical exponent beta of the staggered magnetization suggesting that the magnetic phase transitions observed are three dimensional in nature. The ac susceptibility exhibits Curie-Weiss behavior above T-N, and departures from this behavior in the ordered state for all the systems studied. The magnetic transitions are clearly evident in the chi(ac) versus T plots, however, no cusp typical of antiferromagnetic ordering was present.
