Enhancement of the magnetoresistive property by introducing disorder in the (La1−xYx)0.7Ca0.3MnO3 compound

Abstract

An extraordinarily large magnetoresistance (MR) has been achieved in La_0.7Ca_0.3MnO₃ by optimal substitution. To explore the origin of this giant enhancement of MR, we have carried out magnetic and magnetotransport measurements of (La_1−xY_x)_0.7Ca_0.3MnO₃ (x = 0, 0.4, 0.5, 0.6, and 1) compounds in detail. Our analysis indicates that the disorder introduced by yttrium substitution plays the crucial role in the magnetoresistive properties in this series. A large MR has been observed in optimally doped (La_0.5Y_0.5)_0.7Ca_0.3MnO₃ (x = 0.5). In this compound, an MR value as high as 1.5 × 10⁷% at a temperature of 50 K and 3.6 × 10⁴% at 80 K has been achieved for an external magnetic field of 90 kOe. Moreover at 80 K, for the x = 0.5 compound, the MR is reversible in nature. The extraordinarily enhanced and large MR value has been described using a phenomenological model of percolation via ferromagnetic clusters.