Synthesis and Physical Properties of Iridium-Based Sulfide Ca1−xIr4S6(S2) [x = 0.23–0.33

Michael Vogl,Martin Valldor,Roman Boy Piening,Dmitri V Efremov,Saicharan Aswartham,Bernd Büchner

doi:10.3390/electronicmat3010004

Abstract

We present the synthesis and characterization of the iridium-based sulfide Ca1−xIr4S6(S2). Quality and phase analysis were conducted by means of energy-dispersive X-ray spectroscopy (EDXS) and powder X-ray diffraction (XRD) techniques. Structure analysis reveals a monoclinic symmetry with the space group C 1 2/m 1 (No. 12), with the lattice constants a = 15.030 (3) Å, b = 3.5747 (5) Å and c = 10.4572 (18) Å. Both X-ray diffraction and EDXS suggest an off-stoichiometry of calcium, leading to the empirical composition Ca1−xIr4.0S6(S2) [x = 0.23–0.33]. Transport measurements show metallic behavior of the compound in the whole range of measured temperatures. Magnetic measurements down to 1.8 K show no long range order, and Curie–Weiss analysis yields θCW = −31.4 K, suggesting that the compound undergoes a magnetic state with short range magnetic correlations. We supplement our study with calculations of the band structure in the framework of the density functional theory.

Highlights

BaNiS2 [1] shows a metalinsulator transition (MIT). This MIT has attracted interest because it is associated with a competition between an insulating antiferromagnetic (AF) phase and a paramagnetic metallic one [2], similar to the case of unconventional superconductors, such as cuprates [3], Fe-based [4], and heavy fermions [5], whereas BaFe2 S3 is a Mott insulator that shows a stripe-type magnetic order below 119 K [6]
Amongst residues of the starting materials, the pattern of an unknown structure was found by X-ray diffraction
We present the synthesis and characterization of iridium-based sulfide Ca1−x Ir4 S6 (S2 )

Summary

Introduction

BaNiS2 [1] shows a metalinsulator transition (MIT) This MIT has attracted interest because it is associated with a competition between an insulating antiferromagnetic (AF) phase and a paramagnetic metallic one [2], similar to the case of unconventional superconductors, such as cuprates [3], Fe-based [4], and heavy fermions [5], whereas BaFe2 S3 is a Mott insulator that shows a stripe-type magnetic order below 119 K [6]. Ternary metal sulfides, such as NiCo2 S4 , have received attention for their catalytic activity in oxygen reduction and evolution reactions [7,8]. Most of these materials are 3d-based sulfur compounds. CuIr2 S4 that has a mixed Ir3+ /Ir4+ metallic phase and undergoes a first-order transition near 230 K to a low-temperature, charge-ordered, diamagnetic, insulating phase [9,10,11]

Results

Discussion

Conclusion