Spin ordering and electronic texture in the bilayer iridate Sr${}_3$Ir${}_2$O${}_7$

Through a neutron scattering, charge transport, and magnetization study, the correlated ground state in the bilayer iridium oxide Sr${}_3$Ir${}_2$O${}_7$ is explored. Our combined results resolve scattering consistent with a high temperature magnetic phase that persists above 600 K, reorients at the previously defined $T_{\text{AF}}=280$ K, and coexists with an electronic ground state whose phase behavior suggests the formation of a fluctuating charge or orbital phase that freezes below $T^{*}\approx 70$ K. Our study provides a window into the emergence of multiple electronic order parameters near the boundary of the metal to insulator phase transition of the $5d$ $J_{\text{eff}}=1/2$ Mott phase.

Figure 1

(a) Temperature dependence of the $ab$-plane resistivity for Sr-327. Also plotted is the $\frac{\partial \ln \rho }{\partial (1/T)}$ vs $T$ showing two peaks at $T_{\text{AF}}$ and $T^{*}$. (b) $I$-$V$ curve of $ab$-plane transport at 300 mK showing voltage biasing into a FEC regime. (c) Current driven, pulsed, $I-V$ measurements as a function of temperature. Solid lines show linear fits to the Ohmic regime at each temperature. The dashed line is a Joule heating model at 30 K as described in the text. (d) Magnetoresistance (MR) ratio as described in the text plotted as a function of temperature showing two well defined minima at the $T^{*}$ and $T_{\text{AF}}$ transitions.

Figure 2

(a) dc-magnetization data for Sr-327 with $H=0.01$ T aligned parallel to the $\mathit{ab}$ plane for both FC (solid symbols) and ZFC temperature sweeps (open symbols). The dashed line shows the mean-field order parameter fit to the net moment from the 280 K transition. The inset shows $M$ vs $H$ sweep at 300 K. (b) Temperature dependence of the peak intensities at (1,0,3) and (1,0,2) magnetic reflections. The solid line is a power law fit to the (1,0,2) order parameter.

Figure 3

Radial $\mathbf{Q}$ scans at 100 and 315 K through the (a) $\mathbf{Q}=(1,0,2)$ and (b) $\mathbf{Q}=(1,0,3)$ reflections. Solid lines are Gaussian fits to the data. (c) $L$ scans across the (1,0,3) peak position showing three-dimensional (3D) superlattice peaks at 100 and 315 K. (d) $\mathbf{Q}$ scans showing the temperature dependence of the (1,0,3) peak.

Figure 4

(a) Rocking scans on a separate crystal showing the temperature dependence of the (1,0,3) peak above 300 K. (b) Temperature dependence of the $a$- and $c$-axis lattice parameters measured at the (2,0,0) and (0,0,4) reflections. Integrated intensities plotted as (c) 100 K with 315 K data subtracted and (d) the total scattering data at 100 K. Data is compared with two simple collinear spin models described in the text.