The magneto-transport and low-field magnetoresistance in double-layer manganites La2-2xSr1+2xMn2O7 with insulating second phase

The double-layer perovskite manganite ceramics with a nominal chemistry La2-2xSr1+2xMn2O7 (LSMO(n = 2)) at x = 0.15 and 0.3 with minor La2O3 insulating phase are prepared using sol-gel method and their magneto-transport and low-field magnetoresistive (LFMR) properties are investigated and compared with those properties of ceramic La0.67Sr0.33MnO3 (LSMO) with minor La2O3 second phase. It is revealed that the ceramic LSMO(n = 2) shows different conduction and magnetic behaviors from ceramic LSMO. It is suggested that the observed LFMR for ceramic LSMO(n = 2) is attributed to the spin-polarized tunneling mechanism although its value is slightly lower than that for LSMO. (C) 2003 Elsevier Science B.V. All rights reserved.