Epitaxial thin films of pyrochlore iridate Bi_{2+x}Ir_{2-y}O_{7-delta}: structure, defects and transport properties

Abstract

While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. Here we report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi2Ir2O7. The films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of Bi_Ir antisite defects, qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.

arXiv commentTo appear in Scientific Reports

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• Topological Properties and Functionalities in Oxide Thin Films and Interfaces
• Robust pinning of magnetic moments in pyrochlore iridates
• Influence of electronic structure parameters on the electrical transport and magnetic properties of $Y_{2-x}B{i}_{x}I{r}_2{O}_7$ pyrochlore iridates
• Suppression of long range magnetic ordering and electrical conduction in Y${}_{1.7}$Bi${}_{0.3}$Ir${}_2$O${}_7$ thin film
• Possible Scale Invariant Linear Magnetoresistance in Pyrochlore Iridates Bi${}_2$Ir${}_2$O${}_7$
• Synthesis of epitaxial magnetic pyrochlore heterojunctions
• Anomalous Proximitized Transport in Metal/Quantum Magnet Heterostructure $\mathrm{B}{\mathrm{i}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7/Y{\mathrm{b}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$
• Probing ice-rule-breaking transition in $\mathrm{D}{\mathrm{y}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$ thin film by proximitized transport and magnetic torque