Spin-orbit tuned metal-insulator transitions in single-crystal Sr₂Ir_1–xRh_xO₄ (0≤x≤1)

Journal Article · Thu Sep 06 00:00:00 EDT 2012 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.86.125105· OSTI ID:1103269

Qi, T. F.; Korneta, O. B.; Li, L.; Butrouna, K.; Cao, V. S.; Wan, Xiangang; Schlottmann, P.; Kaul, R. K.; Cao, G.

Sr₂IrO₄ is a magnetic insulator driven by spin-orbit interaction (SOI) whereas the isoelectronic and isostructural Sr₂RhO₄ is a paramagnetic metal. The contrasting ground states have been shown to result from the critical role of the strong SOI in the iridate. Our investigation of structural, transport, magnetic, and thermal properties reveals that substituting 4d Rh⁴⁺ (4d⁵) ions for 5d Ir⁴⁺ (5d⁵) ions in Sr₂IrO₄ directly reduces the SOI and rebalances the competing energies so profoundly that it generates a rich phase diagram for Sr₂Ir_1–xRh_xO₄ featuring two major effects: (1) Light Rh doping (0 ≤ x ≤ 0.16) prompts a simultaneous and precipitous drop in both the electrical resistivity and the magnetic ordering temperature TC, which is suppressed to zero at x = 0.16 from 240 K at x = 0. (2) However, with heavier Rh doping [0.24 < x < 0.85 (±0.05)] disorder scattering leads to localized states and a return to an insulating state with spin frustration and exotic magnetic behavior that only disappears near x = 1. The intricacy of Sr₂Ir_1–xRh_xO₄ is further highlighted by comparison with Sr₂Ir_1–xRu_xO₄ where Ru⁴⁺ (4d⁴) drives a direct crossover from the insulating to metallic states.

• Sponsoring Organization: USDOE
• OSTI ID: 1103269
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Vol. 86 Journal Issue: 12; ISSN 1098-0121
• Publisher: American Physical Society
• Country of Publication: United States
• Language: English