Colossal Magnetoresistance of A-Site Ordered (NdBaSm)2Mn2O6 at Ambient Temperature

Abstract

The behavior of the A-site ordered (Nd(1-L)PrL)(1-x)Ba(1-y)Sm(x+y)Mn2O6 shows remarkable dependence on y. Whereas the effect of the increase in x and L is understandable using the phase diagram, the change with y shows anomalous behavior. Charge and orbital (CO) ordering is absent in the host NdBaMn2O6, appears with x, increases with y initially but disappears when y becomes greater than 0.1. The magnetoresistance (MR) at room temperature is maximum for a composition that shows high CO ordering temperature. Such a composition provides MR at room temperature, which is an order of magnitude larger than the value obtained in earlier studies. In the absence of CO ordering for y≥0.1, MR is maximum when the composition is close to the phase boundary separating it from the metallic phase, although the maximum MR occurs at a lower temperature. Nevertheless, a room-temperature MR of 700% has been obtained in this case also. The phenomenon of the cusp-like increase in MR at the metal-insulator phase boundary is explained and experimental support is obtained.