Metal-insulator transition in colossal magnetoresistance materials

Abstract

We report on resistivity measurements in ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ and ${\mathrm{Nd}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ thin films in order to elucidate the underlying mechanism for the colossal magnetoresistance behavior. The experimental results are analyzed in terms of quantum phase-transition ideas to study the nature of the metal-insulator transition in manganese oxides. Resistivity curves as functions of magnetization for various temperatures show the absence of scaling behavior expected in a continuous quantum phase transition, which leads us to conclude that the observed metal-insulator transition is most likely a finite temperature crossover phenomenon.