Study of A-site ordered PrBaMn2O6−δmanganite properties depending on the treatment conditions

The effect of treatment conditions on the magnetic and magnetotransport properties of A-site ordered PrBaMn2O6−δ manganites is examined. The parent oxygen-stoichiometric A-site ordered PrBaMn2O6 samples were prepared from oxygen-stoichiometric A-site disordered Pr0.50Ba0.50MnO3 ones by using a 'two-step' synthesis method. The most significant structural feature of the A-site ordered manganites is that the MnO2 sublattice is sandwiched by two kinds of rock-salt layers, PrOx and BaO. The oxygen-stoichiometric A-site ordered PrBaMn2O6 demonstrates a ferromagnetic metal to paramagnetic insulator transition with the Curie point at about 320 K. These compounds are stable in air up to 1300 °C. The A-site ordered PrBaMn2O6 samples were next reduced in flowing argon as well as being treated under high pressure conditions. The reduction of the A-site ordered PrBaMn2O6 samples leads to the appearance of an antiferromagnetic state with a Neel point of about 140 K, while the A-site order remains. Upon high pressure treatment the degree of A-site order decreases, which reduces TC to 180 K. The magnetotransport properties of A-site ordered manganites treated under different conditions are discussed in terms of the manganese valence, oxygen content and degree of A-site order.