Inhomogeneous magnetic state in manganites-experimental aspects

The crystal and magnetic structure as well as elastic, magnetic, and electrotransport properties of La0.88MnOx (2.82⩽x⩽2.96) and Nd1−xCaxMnO3 (0⩽x⩽0.2) manganites have been investigated as a function of Mn4+ content by X-ray, neutron diffraction, Young's modulus, magnetization, and resistivity measurements. The gradual transition from an orbitally ordered state to an orbitally disordered one is observed with increasing temperature or Mn4+ content. The magnetic properties of the samples have been found to correlate with the type of orbital state. The dynamic orbital correlations favor ferromagnetic state, while A-type antiferromagnetic state is typical for the static Jahn-Teller distortions. The properties are discussed in the framework of the structurally driven phase separation model.