Non-monotonic effect of the electronic transport and magnetic properties in a Sm-doped Sr_2−x Sm_xIrO₄system

¹ College of Electronic and Optical Engineering, Nanjing University of Posts and Telecommunications Nanjing, Jiangsu 210023, China
² School of Science, New Energy Technology Engineering Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications - Nanjing, Jiangsu 210023, China
³ National Laboratory of Solid State Microstructures, Nanjing University - Nanjing 210093, China

^(a) chengj@njupt.edu.cn
^(b) zhwang@nju.edu.cn

Received: 3 June 2018
Accepted: 7 October 2018

Abstract

Sr₂IrO₄ has been shown to host a novel 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 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 non-monotonic variation of resistivity with x. 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 Sr_2−xSm_xIrO₄ 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 Ir⁴⁺-O-Ir⁴⁺ and enhanced Sm³⁺-O-Ir⁴⁺ exchange interactions.