Praseodymium deficiency effects on the physical properties of Pr_1.2–x□_xSr_1.8Mn₂O₇ bilayer manganese oxides

Abstract

The praseodymium deficiency effects on the structural, magnetic and electrical properties of the lacunar bilayers manganese oxides Pr 1.2-x x Sr 1.8 Mn 2 O 7 (0 ≤ x ≤ 0.15) were studied. Rietveld refinements of the X-ray diffraction patterns show that all our samples are single phase and crystallize in the tetragonal structure with I4/mmm space group. All our samples exhibit a paramagnetic-ferromagnetic transition on cooling. The praseodymium deficiency leads to a decrease of the Curie temperature. Resistivity measurements as a function of temperature show that only the parent sample Pr 1.2 Sr 1.8 Mn 2 O 7 exhibits a semiconductingmetallic transition with decreasing temperature.