Search

Double manganite PrBaMn2O6 with ordered alternate stacking of PrMnO3/BaMnO3 layers attracts a special interest due to presence of two magnetic phase transitions close to room temperature; that makes it perspective magnetocaloric and magnetoresistive material. Besides the magnetic phase transition, the structural transition accompanied with the elongation of the a-axis and the contraction of the c-axis was experimentally detected. The origin of structural phase transition is studied by X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), IR absorption spectroscopy, magnetometry and dynamical mean-field theory (DMFT) for electronic structure calculations. It is found that the structural phase transition is caused by splitting of eg-doublet states due to the tendency towards orbital ordering at the metal-insulator phase transition.

For double manganites PrBaMn2O6 with different degree of A-site ordering, magnetic and optical properties in near-IR range were studied. Full ordered manganite is characterized by antiferromagnetic state at low temperatures; magnetic phase transition from antiferromagnetic to ferromagnetic state occurs near TN = 262 K and to paramagnetic state near TC = 305 K. Partially disordered manganite consists of few fractions with different state of A-site ordering and shows the transition from ferromagnetic state to paramagnetic one at 190 K. For disordered manganite weak ferromagnetic contribution is observed below 130 K. The optical density spectra and the temperature dependences of light transmission indicate a change in behavior of the charge carrier system (metal–insulator transition) near the magnetic phase transitions. The magnetotransmission effect was measured for the first time in double manganites PrBaMn2O6. Spectral dependence of magnetotransmission lets associate this effect with an increase in the fraction of delocalized charge carriers when a magnetic field is applied.