Enhanced insulating state and diluted Ir⁴⁺ spin orders in Ir-vacant Sr₂Ir_1−xO₄ systems

¹ School of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications Wenyuan road 9, 210023, Nanjing, PRC
² College of Science, Center of Advanced Functional Ceramics, Nanjing University of Posts and Telecommunications Wenyuan road 9, 210023, Nanjing, PRC
³ Department of Physics, Nanjing University, National Lab for Solid State Microstructures - 210093, Nanjing, PRC

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

Received: 27 June 2017
Accepted: 15 December 2017

Abstract

A series of polycrystalline samples of Sr₂Ir_1−xO₄  has been synthesized by the solid-state reaction method. The evolution of the structure and the physical properties are studied with increasing Ir vacancies. Ir vacancies induce a significant structural change, especially the decrease of the Ir-O-Ir bond angle. This, together with the increasing disorder causes the increasing of resistivity. The sharp decrease of the total moment is attributed to the reduced number of magnetic Ir⁴⁺ ions and the weakened exchange interactions resulting from the diluted Ir⁴⁺ ions. The enhancement moment at lower temperature is probably due to the long-way exchange interactions of diluted Ir⁴⁺ spins via Ir⁵⁺ ions. The suppression of the antiferromagnetic transition contrasting to the enhancement of the insulating state may suggest that magnetic order is not the origin of the gap opening in the Sr₂IrO₄ system.