Response of the Charge Subsystem to Phase Transitions in Double Manganites LnBaMn2O6

We study the structural, magnetic, and optical properties of double manganites LnBaMn 2 O 6 with Ln = Pr, Nd, Sm, Nd 1 – x Sm x ( x = 0.25, 0.5, 0.75). Analysis of the temperature dependences of transmission in the near IR range has shown the difference in the responses of the charge subsystem for different types of charge/orbital ordering in the system. In PrBaMn 2 O 6 manganite, the orbital ordering of the type leads to an insulator state at low temperatures. The charge subsystem of manganites NdBaMn 2 O 6 , Nd 0.75 Sm 0.25 BaMn 2 O 6 , and Nd 0.5 Sm 0.5 BaMn 2 O 6 is sensitive to the orbital ordering type: in the temperature interval T CO2 < T < T CO1 , where pairwise alignment of layers with / ordered orbitals is realized, the semiconductor character of charge carriers is observed, while upon a transition to the layer-by-layer alignment of orbitally ordered layers for T < T CO2 , charge carriers are of the metal character. In manganites Nd 0.25 Sm 0.75 BaMn 2 O 6 and SmBaMn 2 O 6 , the absence of clearly manifested metal nature of the charge subsystem at T < T CO2 is associated with the formation of the antiferromagnetic ordering of the CE type.