Critical linear and nonlinear responses and evidence for two-phase coexistence in a Nd0.77Ba0.23MnO3 single crystal

We present the data on dynamic linear and nonlinear susceptibilities (second and third harmonics of magnetization) in the critical paramagnetic region for weakly doped manganite Nd 0.77 Ba 0.23 MnO 3 . It has a pseudocubic structure both at room temperature and below the Curie temperature, remaining in an insulating state below T C . The coexistence of two magnetic phases is found below T 146.7 K > T C 124.1 K. The critical behavior of the major phase is in good quantitative agreement with the scaling theory for Heisenberg ferromagnets. The second phase is found to spontaneously magnetize. The unexpected appearance of the new phase in the paramagnetic region is discussed on the basis of recent ideas on phase separation in the weakly and moderately doped manganites.