Metal-insulator transition below the Curie temperature in layered manganites

In contrast to the traditional viewpoint that a metal-insulator transition (MIT) occurs just at the resistivity peak temperature T-p, we propose that in perovskite manganites with temperature-dependent disorder, T-MI at which the MIT occurs may be well below the Curie temperature T-C(similar or equa l to T-p). At temperatures between T-MI and T-C, due to a decrease in local ization length upon heating, the resistivity of the localized electrons beh aves with metallic temperature dependence. Only above T-C does the resistiv ity exhibit semiconductorlike temperature behavior. Such an idea that the M IT occurs below T-C can account for the anomalous resistivity behavior in t he layered manganite crystal La2-2xSr1+2xM2O7 with x=0.3. [S0163-1829(98)02 845-8].