Effect of uniaxial pressure on charge transport in the layered manganite La_1.25Sr_1.75Mn₂O₇

Abstract

The effect of uniaxial pressure on resistivity along the ab plane (ρ_ab) and c axis (ρ_c) in single crystals of bilayer manganite La_1.25Sr_1.75Mn₂O₇ has been investigated. A prominent finding is the asymmetric role of pressure on charge transport phenomenon. With increasing pressure along the c axis, ρab decreases and the metal-insulator (MI) transition temperature shifts towards higher temperature at the rate of 46K/GPa. In contrary to this, ρc increases and the MI transition temperature decreases with increasing pressure along the ab plane. The resistivity ratio ρ_c/ρ_ab is quite large, increases with pressure, and shows a peak at around the MI transition. We believe that the unusual behavior of transport properties is related to the Mn−O−Mn linkage between MnO₂ layers and the spin reorientation from the c axis to the basal plane and vice versa with pressure.