The nonlinear magnetic properties of the pseudocubic Nd0.77Ba0.23MnO3 single crystal in the critical paramagnetic region and phase separation

The second magnetization harmonic was studied for a moderately doped Nd_0.77Ba_0.23MnO₃ neodymium manganite single crystal in parallel constant and harmonic magnetic fields in the critical paramagnetic region. According to the neutron and X-ray diffraction data, the crystal was crystallographically single-phase and had a pseudocubic structure both at room temperature and below the Curie point T _C=124.1 K. Although the specific resistance of this compound had a singularity near T _C and exhibited giant magnetoresistance, it remained an insulator in the ferromagnetic state. Nonlinear response measurements in the T _C<T<T _*≈146.7 K paramagnetic region were indicative of the existence of two magnetic phases. Above T _*, the crystal was magnetically single-phase, and its critical behavior was well described by dynamical similarity theory for isotropic 3D ferromagnets. The unexpected appearance of a new magnetic phase in the structurally homogeneous crystal was discussed based on phase separation ideas; such a phase separation could occur in moderately doped cubic manganites experiencing orbital ordering.