Abstract
We present the effect of vacancy and Na doping on the critical behavior in La0.8Pb0.2MnO3 via dc magnetization measurements. Critical exponents values for La0.8Pb0.2MnO3 match well with those predicted for the three-dimensional Heisenberg model. The vacancy in La0.8Pb0.1 square 0.1MnO3 does not alter the Heisenberg universality class. However, the critical isotherm exponent is slightly larger than predicted consistent with the presence of a Griffiths phase. For La0.8Pb0.1Na0.1MnO3, we found that the critical exponents values are in a close agreement with those predicted for the mean-field theory. The reason for this behavior may be long-range interactions between spins in this system. (C) 2011 Elsevier B.V. All rights reserved.