Linear and nonlinear critical magnetic properties and transport in Nd0.75Ba0.25MnO3 single crystal:: evidence for its anomalous critical behavior near TC

The data on the resistance and magnetoresistance (MR) as well as measurements of the linear and nonlinear susceptibilities are presented for a Nd0.75Ba0.25MnO3 single crystal with the Curie temperature T-C approximate to 129 K. Although this compound remains insulating in the ferromagnetic state, its resistance has an anomaly near T-C and it reveals the colossal magnetoresistance. The data on the magnetic response are well described by the dynamic scaling theory for 3D isotropic ferromagnets in the paramagnetic critical region at tau > tau* approximate to 0.11, tau = (T - T-C)/T-C. Below tau* an anomalous critical behavior is found that suggests the coexistence of two magnetic phases. This behavior is discussed in terms of a phase separation which can occur in the moderately doped manganites exhibiting an orbital ordering. (C) 2004 Elsevier Ltd. All rights reserved.