Colossal magnetoresistance properties of the manganese perovskites La0.7-xYxCa0.3MnO3-delta

Colossal magnetoresistance (CMR) properties have been evidenced for the manganese perovskites La0.7-xYxCa0.3MnO3-delta with 0.01 less than or equal to x less than or equal to 0.20. This system is compared to the manganites Pr0.7Ca0.3-xSrxMnO3-delta that exhibit the same Mn(III)/Mn(IV) ratio. Like for this second system, one observes that the transition temperature T-1 increases as the size of the interpolated cation increases from 75 to 225 K. This comparison demonstrates that the Mn(III)-Mn(IV) mixed valence (hole carrier density) and the size of the interpolated cations are the two main factors that govern the transition temperature T-1. However, the CMR effect characterized by the resistance ratio (RR) R(0)/R(B) (R(0) resistance in zero magnetic field and R(B) resistance in a magnetic field, B=5 T) is much lower than that observed for the Pr manganites. The highest RR value is of 40 for La-Y phases for T=120 K (x=0.10) against 2.5x10(5) for the Pr phase for T=88 K (x=0.05). Thus, it is suggested that the electronic configuration of the interpolated cation may play an important role in the amplitude of the CMR effect. (C) 1996 American Institute of Physics.