Magnetotransport property of layered manganites (La,Sr,Ca)(3)Mn2O7

We report the magnetotransport properties of two series of Sr3Ti2O7 type ma nganites, La2-2xSr1-2xMn2O7 and Ln(1.4)Sr(1.6-x)Ca(x)Mn(2)O(7). The former manganites show magnetotransport properties, which depend on x, that is, th e cal pier number. They show insulator to metal transition, when reducing t emperature. The transition temperature increases with x up 0.4 and decrease s with x exceeding 0.4. Around their transition temperature, they also show giant magnetoresistance, which decreases monotonically with increasing x. The latter manganites also show the electric transition temperature, which decreases with increasing x, that is, decreasing lattice constants. The gia nt magnetoresistance around transition temperature decreases monotonically with decreasing lattice constants. The magnetotransport properties of Sr3Ti 2O7 type manganites are sensitive to carrier number and lattice constants. (C) 1999 Elsevier Science Limited. All rights reserved.