Electronic and magnetic properties in three-component manganite films – the role of ordered interfaces and ionic size effects

The mixed-valent manganite, La_1-xSr_xMnO₃, with x= 1/3 has been widely studied for its colossal magneto-resistive properties arising from the double exchange interaction. This material can be grown in thin-film form as a random alloy or an ordered superlattice. Here we grow films replacing 50% of the La with Y to make La_1/3Y_1/3Sr_1/3MnO₃ as both random alloys where La, Sr, and Y randomly occupy the A-site and ordered superlattices where the supercells comprise of single unit cells of LaMnO₃, YMnO₃, and SrMnO₃ stacked in sequence_. While electronically La and Y are very similar, as both tend to be in a 3+ oxidation state in the crystal, we find contrastingly different electronic transport. The Y-substituted films exhibit a suppression of the metal-to-insulator transition compared to that of La_1/3Sr_2/3MnO₃. While the suppression is observed in both the ordered superlattice and the random alloy, we find it notably more amplified in the random alloy sample. We will discuss how ionic size effects and ordered interfaces affect the electronic and magnetic properties of these samples.