Reentrant spin glass behavior and magnetodielectric coupling of an Ir-based double perovskite compound, LaCoIrO.

The structural, magnetic, electrical and dielectric properties of an Ir-based double perovskite compound, LaCoIrO, have been investigated. The sample undergoes a paramagnetic-ferromagnetic transition at T, followed by a reentrant spin-glass transition at lower temperatures. The reentrant spin glass state in LaCoIrO is associated with the competitions of the antiferromagnetic coupling between Ir and Co ions and the ferromagnetic clusters. LaCoIrO shows a semiconducting transport behavior in the temperature range 65 to 360 K and the transport behavior can be well described by the three-dimensional Mott variable range hopping conduction mechanism. Moreover, a strong frequency dependence of dielectric constant behavior for LaCoIrO is observed and the dielectric relaxation can be ascribed to the electron hopping between different transition metal ions. In addition, the isothermal magnetic field dependent dielectric constant measurements show that a clear magnetodielectric coupling effect exists in LaCoIrO at low temperatures.