Ferroelectric Electric Field Control of Magnetotransport Properties in Ultrathin Sr₂IrO₄ Films

We report the study of the ferroelectric field control of the magnetotransport properties in 5d iridate Sr₂IrO₄ (SIO214) films. High quality epitaxial heterostructures composed of 150 nm PbZr_0.2Ti_0.8O₃ (PZT) and 2.6-5.2 nm SIO214 were fabricated on (001) LSAT and LaAlO₃ substrates via off-axis RF magnetron sputtering. Polarization switching in PZT enables nonvolatile modulation of the channel resistance. For the 5.2 nm SIO214 on LSAT, the resistance switching ratio increases from ~10% at 300 K to ~120% at 2 K. The low-temperature conductance shows a natural logarithmic dependence for both polarization states, suggesting a 2D behavior. The low temperature magnetoconductance (MC) can be described by weak localization and weak antilocalization, with the latter consistent with the strong spin-orbit coupling (SOC) in iridates. Fitting the MC data with the Maekawa-Fukuyama model shows the inelastic (spin–orbit) scattering length for the polarization-up state is about 25% (10%) longer than those in the polarization-down state at 5 K. We discuss the intrinsic and extrinsic scattering contributions to this modulation. We also observe nonvolatile modulation of the out-of-plane anisotropic magnetoresistance at low temperatures (5–30 K), which signals the ferroelectric field effect control of magnetic anisotropy.