The Study Of Sr-site Sm Doping Of Spin-orbit-couple Mott Insulater Sr₂IrO₄

The 5d transition-metal oxide,Sr₂IrO₄,attracted intensive attention in condensed matter physics and materials science.There is a frangible counterpoise between Coulomb interactions,spin-orbit-coupling?SOC?,and crystal field splitting in Sr₂IrO₄ system,which have already been considered as the candidate for exotic physical phenomena and recently attracts considerable attention in high-temperature superconductivity.So far,a large number of electron-and hole-doped experiments have not found any unconventional superconductivity in Sr₂IrO₄ system,but some of the exotic physical properties of the system still attracted intensive attention.By modulating the exchange interaction of the system,many exotic magnetic phenomena can be observed in the doped Sr₂IrO₄ system,especially in the study of magnetic element doped material.The study of doping in Sr-site remains at the initial stage,compared with that of doping in Ir-site.Therefore,it is necessary to conduct a more in-depth study of the doping effect in Sr-site,which is crucial for a better understanding of the Sr₂IrO₄ system.Polycrystalline samples of Sr-site doped Sr₂-_xSm_xIrO₄ were synthesized through the conventional solid state reaction method.The elemental composition,phase purity,crystal structure and chemical valence of the Sr₂-_x Sm_x IrO₄ samples were characterizated by many commonly used methods,such as EDS,XRD,Rietveld refine,Raman spectrum and XPS.The electrical resistivity and magnetic susceptibility of the samples were measured by PPMS,and the electrical and magnetic properties of the samples were analyzed.Sm-doped samples still retain the insulating behavior,whose conduction mechanism can be fitted by three different modes.With the increase of Sm-doping concentration x,the resistivity firstly decreases for x?0.1 and then increases.The nonmonotonic variation of resistivity with x could be attributed to the increment of the Ir-O-Ir bond angle,combined with the modulation of the regularity of IrO₆ octahedra.On the other hand,there are two types of magnetic exchange interactions(i.e.,Ir⁴⁺-O-Ir⁴⁺and Sm³⁺-O-Ir⁴⁺)in the Sm-doped Sr₂-_x Sm_xIrO₄ system.Antiferromagnetic component is greatly suppressed in the low concentration x?x?0.125?and then an ascension emerges in the high concentration x,which is attributable to the competition between the weakened Ir⁴⁺-O-Ir⁴⁺and enhanced Sm³⁺-O-Ir⁴⁺exchange interactions.