Spin dynamics in IrSr2Sm1.15Ce0.85Cu2O10: Complex magnetic behavior in a layered iridocuprate

A muon spin rotation (mu SR), neutron, and synchrotron diffraction study of the reentrant spin-glass material IrSr2Sm1.15Ce0.85Cu2O10 is presented. The synthesis has been optimized, and Rietveld refinement of the diffraction patterns shows no sign of the previously reported Ir/Cu cation exchange but confirms the structure along with the disordered tilts and rotations of IrO6 octahedra. The zero-field-mu SR response indicates a complex temperature dependence to the magnetism with multiple transitions that are confirmed to be bulk phenomena. Consecutive transitions are reported at t(1) = 140, t(2) = 20, and t(3) = 6 K. The broad transition at 140 K is assigned to antiferromagnetic ordering of Ir4+ spins with a stripe spin structure. The low-temperature transitions are a result of antiferromagnetic ordering of Cu2+ spins followed by the freezing of a disordered Ir spin component, further evidenced by a strong damping of the oscillation amplitude below 6 K. These observations confirm the bulk nature of the previously reported reentrant spin-glass behavior of this complex magnetic system.