Colossal Isotope Shift of the Metal-Insulator Transition Temperature in Epitaxial Thin Films of (La1-y Pry)0·7Ca0·3MnO3

Abstract

A colossal shift of the maximum resistivity temperature induced by oxygen isotope exchange was registered for 60 nm thick films of the solid solution La_0·35Pr_0·35Ca_0·3MnO₃ on perovskite substrates. The magnitude of the effect depends on lattice strain resulting in the largest shift for the film on LaAlO₃: the ¹⁶O sample showed a metal-insulator transition at 182 K, whereas the ¹⁸O sample was insulating down to 4·2 K, which is the highest difference ever reported for CMR manganites. An XRD and Raman spectrometry study indicates no difference in chemical composition or structure for the ¹⁸O and ¹⁶O samples at room temperature. The results are consistent with the model coupling the metal-insulator transition in the perovskite manganites to the lattice dynamics.