Colossal magnetoresistance properties of the manganese perovskites La0.7−xYxCa0.3MnO3−δ

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Abstract
Colossal magnetoresistance (CMR) properties have been evidenced for the manganese perovskites La0.7−xYxCa0.3MnO3−δ with 0.01≤x≤0.20. This system is compared to the manganites Pr0.7Ca0.3−xSrxMnO3−δ that exhibit the same Mn(III)/Mn(IV) ratio. Like for this second system, one observes that the transition temperature T1 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 T1. However, the CMR effect characterized by the resistance ratio (RR) R0/RB (R0 resistance in zero magnetic field and RB 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 2.5×105 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.