Temperature evolution of magnetic and transport behavior in 5dMott insulator Sr₂IrO₄: significance of magneto-structural coupling

Abstract

We have investigated the temperature evolution of magnetism and its interrelation with structural parameters in the perovskite-based layered compound Sr2IrO4, which is believed to be a J(eff) = 1/2 Mott insulator. The structural distortion plays an important role in this material and induces a weak ferromagnetism in an otherwise antiferromagnetically ordered magnetic state with a transition temperature around 240 K. Interestingly, at low temperatures, below around 100 K, a change in the magnetic moment has been observed. Temperature dependent x-ray diffraction measurements show that sudden changes in structural parameters around 100 K are responsible for this. Resistivity measurements show insulating behavior throughout the temperature range across the magnetic phase transition. The electronic transport can be described with Mott's two-dimensional variable range hopping (VRH) mechanism, however, three different temperature ranges are found for VRH, which is a result of varying the localization length with temperature. A negative magnetoresistance (MR) has been observed at all temperatures in contrast to positive behavior generally observed in strongly spin-orbit coupled materials. The quadratic field dependence of MR implies the relevance of a quantum interference effect.

Structural, Magnetization and Spin Wave Analysis in Layered 5d Iridate Sr2IrO4

“…as calculated in Bhatti etal. [9] whereas the measure µ H is close to the reported vales in earlier reports [3,4,9] but the value is very low then the expected value which is due to the canted spin arrangement of this material. Further the thermal demagnetization shows the spin wave is excitation at low temperature and long range magnons are active in this material.…”

“…We have followed the same sample preparation procedure reported elsewhere. [9,10,11] The phase purity of the sample has been checked using powder x-ray diffraction (XRD) with a Rigaku MiniFlex diffractomer with CuKα radiation. The structural analysis is done on XRD data using FullProof software.…”

Structure, magnetism, and transport properties for Ca doping in Sr2IrO4

“…Resistivity show different temperature-dependence relationships in 200-300 K, 100-200 K and 10-100 K regions. Previous temperature dependent XRD measurements show a sudden change in structural parameters at ∼ 100 K. 20 Thermoelectric power measurements denote the activation of minority carriers through an energy gap also at ∼ 100 K. 18 Temperature dependent optical spectroscopy indicates an inflection point in the optical gap at ∼ 200 K. 21 This anomalous temperature may be coupled to the magnetic ordering temperature ∼ 240 K. Fig. 3(b) clearly shows that the resistivity follows a logarithmic dependence of temperature in the high-temperature region (200-300 K), which can be described by the function ρ (T ) = ρ 0 exp (−αT ).…”

“…The room temperature resistivity of Sr 2 IrO 4 is about 5Ω•cm, approaching to previous reports. 7,19,20 The value of resistivities decreases with Ca doping. The decrease is more significant at the low temperature region.…”

Crystal structure and physical properties of the Sr-vacant spin-orbit-coupling induced Mott insulator Sr2−IrO4

“…In the case of hole doping (V g o0), a persistent insulating state is observed, which is consistent with our result. However, it is contradictory that the resistance in the low temperature region follows the 2D-VRH model, which has also been reported by Noor Bhatti [36]. It seems that this problem is in highly debates.…”