The 'dark phase' in SrIrRhOrevealed by Seebeck and Hall measurements.

It was found that, although isovalent, Rh substituted for Ir in SrIrOmay trap one electron inducing effective hole doping of Ir sites. Transport and thermoelectric measurements on SrIrRhOsingle crystals presented here reveal the existence of an electron-like contribution to transport, in addition to the hole-doped one. As no electron band shows up in ARPES measurements, this points to the possibility that this hidden electron may delocalize in disordered clusters.

Optical Signature of a Crossover from Mott- to Slater-Type Gap in Sr_{2}Ir_{1-x}Rh_{x}O_{4}.

With optical spectroscopy we provide evidence that the insulator-metal transition in Sr_{2}Ir_{1-x}Rh_{x}O_{4} occurs close to a crossover from the Mott- to the Slater-type. The Mott gap at x=0 persists to high temperature and evolves without an anomaly across the Néel temperature, T_{N}. Upon Rh doping, it collapses rather rapidly and vanishes around x=0.

Time-reversal symmetry breaking hidden order in Sr(Ir,Rh)O.

Layered 5d transition iridium oxides, Sr(Ir,Rh)O, are described as unconventional Mott insulators with strong spin-orbit coupling. The undoped compound, SrIrO, is a nearly ideal two-dimensional pseudospin-1/2 Heisenberg antiferromagnet, similarly to the insulating parent compound of high-temperature superconducting copper oxides. Using polarized neutron diffraction, we here report a hidden magnetic order in pure and doped Sr(Ir,Rh)O, distinct from the usual antiferromagnetic pseudospin ordering.

Magnetic critical properties and basal-plane anisotropy of Sr₂IrO₄.

The anisotropic magnetic properties of Sr2IrO4 are investigated, using longitudinal and torque magnetometry. The critical scaling across T(c) of the longitudinal magnetization is that expected for the 2D XY universality class. Modeling the torque for a magnetic field in the basal plane, and taking into account all in-plane and out-of-plane magnetic couplings, we derive the effective fourfold anisotropy K4 ≈ 1 × 10(5) erg mol(-1).