Orbital Ordering Structures in (Nd,Pr)0.5Sr0.5MnO3 Manganite Thin Films on Perovskite (011) Substrates

TL;DR

This study investigates the orbital ordering in (Nd,Pr)0.5Sr0.5MnO3 manganite thin films on different substrates, revealing how structural variations influence electronic phases and orbital orderings, with implications for understanding their ground states.

Contribution

It provides a detailed structural and electronic phase diagram of manganite thin films on (011) substrates, highlighting the relationship between lattice parameters, orbital ordering, and ground state properties.

Findings

NSMO films exhibit antiferro-orbital order at low temperature.

PSMO films show ferro-orbital order on LSAT and no orbital order on STO.

Metallic ground state occurs only in films with a narrow A-site ion radius.

Abstract

Structural study of orbital-ordered manganite thin films has been conducted using synchrotron radiation, and a ground state electronic phase diagram is made. The lattice parameters of four manganite thin films, Nd0.5Sr0.5MnO3 (NSMO) or Pr0.5Sr0.5MnO3 (PSMO) on (011) surfaces of SrTiO3 (STO) or [(LaAlO3){0.3}(SrAl0.5Ta0.5O3){0.7}] (LSAT), were measured as a function of temperature. The result shows, as expected based on previous knowledge of bulk materials, that the films' resistivity is closely related to their structures. Observed superlattice reflections indicate that NSMO thin films have an antiferro-orbital-ordered phase as their low-temperature phase while PSMO film on LSAT has a ferro-orbital-ordered phase, and that on STO has no orbital-ordered phase. A metallic ground state was observed only in films having a narrow region of A-site ion radius, while larger ions favor ferro-orbital-ordered structure and smaller ions stabilize antiferro-orbital-ordered structure. The key to the orbital-ordering transition in (011) film is found to be the in-plane displacement along [0-1 1] direction.