Spin-orbit coupling (SOC) is found to be crucial for understanding the magnetic and electronic properties of $5d$ transition metal oxides. In $5d$ systems, with ${\mathrm{Ir}}^{5+}$ ions, where ideally a nonmagnetic $J=0$ ground state is expected to be stabilized in the presence of strong SOC, often spontaneous moments are generated due to hopping induced superexchange. This effect is more pronounced when the Ir atoms are close by, as in systems with ${\mathrm{Ir}}_2{\mathrm{O}}_9$ dimers in $6H{\mathrm{Ba}}_{3}M{\mathrm{Ir}}_2{\mathrm{O}}_9$ compounds where magnetism is an outcome of complex Ir-O-Ir exchange paths, and is strongly influenced by the presence of local distortions. We find that subtle variations in the local structure of ${\mathrm{Ba}}_{3}M{\mathrm{Ir}}_2{\mathrm{O}}_9$ ($M$ = Mg, Sr, and Ca) lead to markedly different magnetic properties. While SOC plays a pivotal role in explaining the insulating ground states of these systems, it is seen that ${\mathrm{Ba}}_3{\mathrm{MgIr}}_2{\mathrm{O}}_9$, having a $P{6}_3/mmc$ symmetry, does not order down to low temperature despite having antiferromagnetic exchange interactions, while ${\mathrm{Ba}}_3{\mathrm{CaIr}}_2{\mathrm{O}}_9$ shows weak dimer-like features and stabilizes in $C2/c^{\prime }$ magnetic configuration with no net moment, and ${\mathrm{Ba}}_3{\mathrm{SrIr}}_2{\mathrm{O}}_9$ possesses a ground state corresponding to the magnetic space group $C{2}^{\prime }/c^{\prime }$ and exhibits ferromagnet-like features.

Spin-orbit coupling (SOC) plays a crucial role in magnetic and electronic properties of $5d$ iridates. In this paper we have experimentally investigated the structural and physical properties of a series of Ir-based double perovskite compounds ${\mathrm{Pr}}_{2-x}{\mathrm{Sr}}_x{\mathrm{MgIrO}}_6(x$ = 0, 0.5, 1; hereafter abbreviated as PMIO, PSMIO1505, and PSMIO). Interestingly, these compounds have recently been proposed to undergo a transition from the spin-orbit-coupled Mott insulating phase at $x=0$ to the elusive half-metallic antiferromagnetic (HMAFM) state with Sr doping at $x=1$. However, our detailed magnetic and electrical measurements refute any kind of HMAFM possibility in either of the doped samples. In addition, we establish that within these ${\mathrm{Pr}}_{2-x}{\mathrm{Sr}}_x{\mathrm{MgIrO}}_6$ double perovskites, changes in Ir-oxidation states ($4+$ for PMIO to $5+$ for PSMIO via mixed $4+/5+$ for PSMIO1505) lead to markedly different magnetic behaviors. While SOC on Ir is at the root of the observed insulating behaviors for all three samples, the correlated magnetic properties of these three compounds develop entirely due to the contribution from local Ir moments. Additionally, the magnetic ${\mathrm{Pr}}^{3+}$ ($4f^2$) ions, instead of showing any kind of ordering, only contribute to the total paramagnetic moment. It is seen that the ${\mathrm{PrSrMgIrO}}_6$ sample does not order down to 2 K despite antiferromagnetic interactions. But, the $d^5$ iridate ${\mathrm{Pr}}_2{\mathrm{MgIrO}}_6$ shows a sharp antiferromagnetic (AFM) transition at around 14 K, and in the mixed valent ${\mathrm{Pr}}_{1.5}{\mathrm{Sr}}_{0.5}{\mathrm{MgIrO}}_6$ sample the AFM transition is shifted to a much lower temperature ($\sim 6$ K) due to weakening of the AFM exchange.

Environmental contamination due to human activities is a worldwide problem that has led to the development of different remediation techniques, including biotechnological approaches such as phytoextraction and phytostabilization. These techniques take advantage of pioneer plants that naturally develop tolerance mechanisms to survive in extreme environments. A multi-technique and multi-disciplinary approach was applied for the investigation of Helichrysum microphyllum subsp. tyrrhenicum samples, bulk soil, and rhizospheres collected from a metal-extreme environment (Zn-Pb mine of Campo Pisano, SW Sardinia, Italy). Zinc, Pb, and Cd are the most abundant metals, with Zn attaining 3 w/w% in the rhizosphere solid materials, inducing oxidative stress in the roots as revealed by infrared microspectroscopy (IR). X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis coupled with synchrotron radiation-based (SR) techniques demonstrate that quartz, dolomite, and weddellite biominerals precipitate in roots, stems, and leaves, likely as a response to environmental stress. In the rhizosphere, Zn chemical speciation is mainly related to the Zn ore minerals (smithsonite and hydrozincite) whereas, in plant tissues, Zn is primarily bound to organic compounds such as malate, cysteine, and histidine molecules that act as metal binders and, eventually, detoxification agents for the Zn excess. These findings suggest that H. microphyllum subsp. tyrrhenicum has developed its own adaptation strategy to survive in polluted substrates, making it a potential candidate for phytostabilization aimed at mitigating the dispersion of metals in the surrounding areas.

Using angular resolved X-ray Photoelectron Spectroscopy (XPS), Magneto Optic Kerr Effect (MOKE) and X-ray Absorption Spectroscopy (XAS), we characterize the structural and magnetic evolution upon annealing of two thin Co films (8 and 9 Monolayers) deposited on Ir(111). The XAS data collected in the near Co K edge region (XANES), interpreted with ab-initio simulations, show that intermixing takes place at the Co-Ir interface. Using a linear combination analysis, we follow the intermixing during the thermally driven diffusion process. At 500 °C, the interface between Co and Ir(111) roughens slightly, but no alloy formation is detected. At 600 °C, the Co film loses integrity and MOKE data show a rearrangement of the magnetic domains. Annealing to higher temperatures results in CoxIr1 − x alloy formation and Ir segregation on the surface.