PbYb(1/2)Nb(1/2)O(3) and PbYb(1/2)Ta(1/2)O(3) single crystals were grown by the flux method. Crystals that were transparent, brown and in the form of an octahedron with well developed (1 1 1) faces and edge dimensions up to 6 mm were obtained. From XPS analysis the following chemical formulas were found: Pb(1.10)Yb(0.35)Nb(0.57)O(2.98) (PYN) and Pb(0.84)Yb(0.83)Ta(0.60)O(2.72) (PYT). This shows that the PYN crystal has a composition that is closer to the nominal one in comparison with that of the PYT crystal. The magnetic results show that the amount of magnetic Yb(3+) is similar for both compounds. Both compounds are Van Vleck paramagnets as a result of the crystal field effect. The excess of ytterbium in PYT is as non-magnetic Yb(2+) situated probably in the lead position due to the ionic radius size and valency similarity. Such ytterbium division into two valencies ensures charge neutrality of the PYT crystal. (C) 2010 Elsevier B.V. All rights reserved.