Bandwidth-limited control of orbital and magnetic orders in half-doped manganites by epitaxial strain

Abstract

The magnetotransport phase diagram of half-doped manganites ${\text{Ln}}_{0.5}{\text{A}}_{0.5}{\text{MnO}}_{3}$ ($\text{Ln}={\text{La}}^{3+}$, ${\text{Nd}}^{3+}$, etc., and $\text{A}={\text{Sr}}^{2+}$, ${\text{Ca}}^{2+}$, etc.) is primarily dictated by the bare conduction bandwith (${W}_{0}$), which itself is controlled by the Mn-O-Mn bond angle, and the carrier concentration. In thin films, epitaxial strain (\ensuremath{\epsilon}) provides an additional tool to tune ${W}_{0}$ by selecting orbital ordering at fixed carrier concentration. Here, we will show that compressive or tensile epitaxial strain on half-doped manganites can have a tremendous and distinct effect on ${\text{La}}_{0.5}{\text{Sr}}_{0.5}{\text{MnO}}_{3}$ (LSMO5) and ${\text{La}}_{0.5}{\text{Ca}}_{0.5}{\text{MnO}}_{3}$ (LCMO5), having broad or narrow ${W}_{0}$, respectively. It is found that in LSMO5, large compressive strain triggers a change from a ferromagnetic and metallic ground state to an insulating and antiferromagnetic state whereas a tensile strain produces an antiferromagnetic but metallic state. In contrast, under strain, LCMO5 remains an antiferromagnetic insulator irrespectively of the strain state. These results illustrate that orbital ordering largely depends on the interplay between ${W}_{0}$ and \ensuremath{\epsilon} and provide a guideline towards responsive manganite layers.