Site dilution and charge disorder effect on physical properties in SrRu1-x Ga x O3.

Here, we report an evolution of structural, magnetic and transport behavior in doped SrRu1-x Ga x O3 (x [Formula: see text] 0.2). The nonmagnetic dopant Ga3+ (3d 10) not only acts for magnetic site dilution in SrRuO3 but also modifies the Ru charge state and electronic density. Our studies show that Ga3+ substitution does not affect the original orthorhombic- Pbnm structure of SrRuO3 which is due to its matching ionic radii with Ru4+ . However, Ga3+ has a substantial effect on the magnetic behavior of SrRuO3 where it decreases both magnetic moment as well as magnetic transition temperature [Formula: see text]. Further, this dilution induces Griffiths phase behavior across [Formula: see text] and cluster-glass behavior at low temperature with higher concentration of doping. The magnetic critical exponent [Formula: see text] increases with x due to this site dilution effect. The Ga3+ induces an insulating state in SrRuO3 with x > 0.05. The charge transport in paramagnetic as well as in insulating state of samples can be well described with Mott's modified variable-range-hopping model. The metallic charge transport just below [Formula: see text] in SrRuO3 obeys Fermi liquid behavior which breaks down at low temperature. We further find a correlation between field dependent magnetoresistance and magnetization through power-law behavior over the series.

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

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.