Nonmonotonic crossover in electronic phase separated manganite superlattices driven by the superlattice period
Studying manganite superlattices [(LCMO) 2n / (PCMO) n ] t made of La 0.625 Ca 0.375 MnO 3 (LCMO) and Pr 0.625 Ca 0.375 MnO 3 (PCMO), we found an unexpected behavior varying the period n. At small n, the ensemble is a three-dimensional ferromagnetic metal due to interfacial charge transfer. At large n , the LCMO layers dominate transport. However, rather than a smooth interpolation between these limits a sharp transport and magnetic anomaly is found at an intermediate critical PCMO thickness n*. Magnetic force microscopy reveals that the phase-separation length scale also maximizes at n* where, unexpectedly, it becomes comparable to that of the (La 1-y Pr y ) 0.625 Ca 0.375 MnO 3 (LPCMO) alloy. Finally, we conjecture the phenomenon originates in a disorder-related length scale: Large charge-ordered clusters as in LPCMO can only nucleate when Pr-rich regions reach a critical size related to n*.