Variation of electrical and magnetic properties in La(0.67-x)GdxCa(0.33)MnO(3) perovskites

We have investigated the variation of electrical and magnetic properties in polycrystalline La0.67-xGdxCa0.33MnO3 with the change of gadolinium conten t. As x increases, we observed a transition from the ferromagnetic state to the canted ferromagnetic state at x = 0.10. The magnetization and conducti vity show considerable thermal hysteresis in the samples with x = 0.10 and 0.15, and magnetoresistance is larger than 65 and 90% over a temperature ra nge similar to 30 K, respectively. Based on the sample with x 0.15 we found an abnormal increase in magnetization in low temperatures which should be attributed to the contribution of paramagnetic gadolinium ions. For x = 0.2 0 and 0.25 samples, insulator conduction has been observed above 80 K, and magnetoresistance similar to 55% has been detected in the sample with x = 0 .20. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.