Nonlinear properties and paramagnet-to-ferromagnet transition in Nd0.7Ba0.3MnO3 single crystal with metallic ground state

We present the results from studying the magnetic properties (linear and nonlinear susceptibilities and the depolarization of polarized neutrons) of Nd1 − x Ba x MnO3 manganite, x = 0.3, with Curie temperature T C ≈ 140 K and dielectric-to-metal transition temperature T DM ≈ 129 K. Its critical behavior corresponds to that of an isotropic 3-D ferromagnet at temperatures above T*≈ 144 K, but a strong nonlinear response in weak magnetic fields and depolarization are observed at temperatures below T*. It is shown that this nontraditional behavior is related to the generation of ferromagnetic clusters in the paramagnetic matrix that form a conducting percolative network at temperatures near T DM.