Non-monotonic effect of the electronic transport and magnetic properties in a Sm-doped Sr _2−x Sm _x IrO ₄ system

Abstract

Sr2IrO4 has been shown to host a novel J eff = 1/2 Mott spin-orbit insulating state with antiferromagnetic ordering. Here, the effects of Sm substitution at Sr-site on structural, electrical and magnetic properties are studied in Sr2IrO4. Sm-doped samples still retain the insulating behavior, but with the increase of Sm-doping concentration x, the resistivity firstly decreases for x ≤ 0.1 and then increases. We found that the increment of the Ir-O-Ir bond angle, combined with the modulation of the regularity of IrO6 octahedra, results in the nonmonotonic variation of resistivity with x. On the other hand, there are two types of magnetic exchange interactions (i.e., Ir 4+ -O-Ir 4+ and Sm 3+ -O-Ir 4+ ) in the Sm-doped Sr2−xSmxIrO4 system. The antiferromagnetic component is greatly suppressed in the low concentration x and then an ascension emerges in the high concentration x, which is attributable to the competition between the weakened Ir 4+ -O-Ir 4+ and enhanced Sm 3+ -O-Ir 4+ exchange interactions.

Suppressed antiferromagnetic ordering and enhanced electrical conduction in doped iridate Sr2−xPrxIrO4

“…In order to understand the transport nature, we have further fitted the resistivity data with different transport models. This fitting is similar to previous reports [13,23,24]. In the high-temperature region (210-290 K), the resistivity is found to be described by the equation:…”

“…where k B is Boltzmann constant, l denotes the localization length, and N(E F ) represents the density of states at the Fermi level. Based on previously estimated value of N(E F ) at 10 28 [13], confirming the validity of the VRH mechanism. We find that T 0 decreases with increasing the Pr concentration.…”

“…Progressive substitution of Ca 2+ onto Sr 2+ sites in (Sr 1−x Ca x ) 2−y IrO 4 + z samples has driven the structure to evolve across a series of structure types, each with insulating ground states [12]. It has been found that Sm-doped Sr 2−x Sm x IrO 4 samples still retain the insulating behavior, but with the increase of Sm doping, the resistivity presents a nonmonotonic electronic transport, as well as magnetic properties [13]. The Rh substitution in Sr 2 Ir 1−x Rh x O 4 has brought about a paramagnetic (PM) and metallic state when the concentration of Rh increases up to a critical value [14,15].…”