Griffiths phase and critical behavior in single-crystal La0.7Ba0.3MnO3:: Phase diagram for La1-xBaxMnO3 (x≤0.33)

Analyses of temperature- and field-dependent ac susceptibility and magnetization data from a colossal magnetoresistive La0.7Ba0.3MnO3 single crystal in terms of scaling behavior yield exponent values of delta=5.5 +/- 0.3 and gamma=1.41 +/- 0.02 (both slightly larger than Heisenberg model predictions), with beta=0.35 +/- 0.04 and a Curie temperature T-C=310 +/- 0.5 K. Detailed investigation of the low-field dc and ac susceptibilities reveals features consistent with the presence of a Griffiths phase (GP)-viz., an inverse susceptibility characterized by chi(-1)proportional to(T-T-C(R))(1-lambda) with lambda=0.67 +/- 0.05. These, combined with previous results, enable a phase diagram summarizing the evolution of the GP with composition in this system to be constructed, and in this context, the possible importance of the variation of the acoustic spin-wave stiffness D with composition is discussed.