  The perovskite SrIrO3 is an exotic narrow-band metal owing to a confluence of
the strengths of the spin-orbit coupling (SOC) and the electron-electron
correlations. It has been proposed that topological and magnetic insulating
phases can be achieved by tuning the SOC, Hubbard interactions, and/or lattice
symmetry. Here, we report that the substitution of nonmagnetic, isovalent Sn4+
for Ir4+ in the SrIr1-xSnxO3 perovskites synthesized under high pressure leads
to a metal-insulator transition to an antiferromagnetic (AF) phase at TN > 225
K. The continuous change of the cell volume as detected by x-ray diffraction
and the lamda-shape transition of the specific heat on cooling through TN
demonstrate that the metal-insulator transition is of second-order. Neutron
powder diffraction results indicate that the Sn substitution enlarges an
octahedral-site distortion that reduces the SOC relative to the spin-spin
exchange interaction and results in the type-G AF spin ordering below TN.
Measurement of high-temperature magnetic susceptibility shows the evolution of
magnetic coupling in the paramagnetic phase typical of weak itinerant-electron
magnetism in the Sn-substituted samples. A reduced structural symmetry in the
magnetically ordered phase leads to an electron gap opening at the Brillouin
zone boundary below TN in the same way as proposed by Slater.
