The iridium double perovskite Sr2YIrO6 revisited: A combined structural and specific heat study

Recently, the iridate double perovskite Sr$_2$YIrO$_6$ has attracted considerable attention due to the report of unexpected magnetism in this Ir$^{5+}$ (5d$^4$) material, in which according to the J$_{eff}$ model, a non-magnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba$_{2-x}$Sr$_x$YIrO$_6$ no indication of magnetic transitions have been found. We present a structural, magnetic and thermodynamic characterization of Sr$_2$YIrO$_6$ single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. Here, we demonstrate the clue role of single crystal X-ray diffraction on the structural characterization of the Sr$_2$YIrO$_6$ double perovskite crystals by reporting the detection of a $\sqrt{2}a \times \sqrt{2}a \times 1c$ supercell, where $a$, $b$ and $c$ are the unit cell dimensions of the reported monoclinic subcell. In agreement with the expected non-magnetic ground state of Ir$^{5+}$ (5d$^4$) in Sr$_2$YIrO$_6$, no magnetic transition is observed down to 430~mK. Moreover, our results suggest that the low temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of $n \sim 0.5(2)$ \%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering.Comment: 20 pages, 10 figure

Iridium double perovskite Sr2YIrO6: A combined structural and specific heat study

© 2017 American Physical Society.Recently, the iridate double perovskite Sr2YIrO6 has attracted considerable attention due to the report of unexpected magnetism in this Ir5+ (5d4) material, in which according to the Jeff model, a nonmagnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba2-xSrxYIrO6 no indication of magnetic transitions have been found. We present a structural, magnetic, and thermodynamic characterization of Sr2YIrO6 single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. As determined by x-ray diffraction, the Sr2YIrO6 single crystals have a cubic structure, with space group Fm3m. In agreement with the expected nonmagnetic ground state of Ir5+ (5d4) in Sr2YIrO6, no magnetic transition is observed down to 430 mK. Moreover, our results suggest that the low-temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of n∼0.5(2)%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering

Observation of heavy spin-orbit excitons propagating in a nonmagnetic background: The case of (Ba,Sr)2YIrO6

We present a combined experimental and theoretical study of the elementary magnetic excitations in Ba2YIrO6 and Sr2YIrO6 - the two most intensively discussed candidates for a new type of magnetic instability caused by exciton condensation. For both materials, high-resolution resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge reveals sharp excitations around 370 and 650 meV energy loss, which we identify as triplet and quintet spin-orbit excitons. While the momentum-dependent RIXS spectra reveal that both the triplet and the quintet propagate coherently within the nonmagnetic background of the singlet sites, these modes remain fully gapped. The Ir-Ir exchange interactions in both double perovskites are therefore not strong enough to overcome the magnetic gap and, hence, our results exclude an intrinsic magnetic instability due to a condensation of magnetic excitations for both Ba2YIrO6 and Sr2YIrO6

Flux growth of Sr_n+1Ir_nO_3n+1 (n=1, 2, ∞) crystals

Single crystals of iridates are usually grown by a flux method well above the boiling point of the SrCl2 solvent. This leads to non-equilibrium growth conditions and dramatically shortens the lifetime of expensive Pt crucibles. Here, we report the growth of Sr2IrO4, Sr3Ir2O7 and SrIrO3 single crystals in a reproducible way by using anhydrous SrCl2 flux well below its boiling point. We show that the yield of the different phases strongly depends on the nutrient/solvent ratio for fixed soak temperature and cooling rate. Using this low-temperature growth approach generally leads to a lower temperature-independent contribution to the magnetic susceptibility than previously reported. Crystals of SrIrO3 exhibit a paramagnetic behavior that can be remarkably well fitted with a Curie-Weiss law yielding physically reasonable parameters, in contrast to previous reports. Hence, reducing the soak temperature below the solvent boiling point not only provides more stable and controllable growth conditions in contrast to previously reported growth protocols, but also extends considerably the lifetime of expensive platinum crucibles and reduces the corrosion of heating and thermoelements of standard furnaces, thereby reducing growth costs.Comment: Accepted in Journal of Crystal Growt

Iridium double perovskite Sr2YIrO6: A combined structural and specific heat study

© 2017 American Physical Society.Recently, the iridate double perovskite Sr2YIrO6 has attracted considerable attention due to the report of unexpected magnetism in this Ir5+ (5d4) material, in which according to the Jeff model, a nonmagnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba2-xSrxYIrO6 no indication of magnetic transitions have been found. We present a structural, magnetic, and thermodynamic characterization of Sr2YIrO6 single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. As determined by x-ray diffraction, the Sr2YIrO6 single crystals have a cubic structure, with space group Fm3m. In agreement with the expected nonmagnetic ground state of Ir5+ (5d4) in Sr2YIrO6, no magnetic transition is observed down to 430 mK. Moreover, our results suggest that the low-temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of n∼0.5(2)%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering

Pemantauan Kualitas Air Sungai Digoel, Distrik Jair, Kabupaten Boven Digoel, Papua

Digoel river have an important role to the human activity and environment in Boven Digoel Regency. Increasing of human and industrial activity around the watershed of Digoel River were suspecious to cause the degradation water quality in Digoel River. This research was done to monitor the impact of the industrial activity to the quality of water in outlet of waste water treatment plant(WWTP) of PT. Korindo to the water quality of Digoel River. Parameter analised are the physical, chemical, organic chemical, microbiology and metal content in water. Analysis of the water quality accordance to PP Nomor 82 Tahun 2001 about water quality managementand water pollution and Permen LH Nomor 5 tahun 2014 about the quality of waste water.The monitoring was conducted in three months at five sampling stasion (river upstream, river down stream, outlet WWTP plywood, outlet WWT workshop, outlet WWTP palm oil) in Districk Jair. The rsult showed, parameter of BOD, COD, phospate, phenol and total coliform in Digoel River exceeded class I of water quality standards. Outlet of plywood WWTP have two parameters that exceed the quality standard which were TSS 15.67 mg/L and phenol 13.33 mg/L.The outlet of WWTP workshop have four pameter exceeded the quality standard which were TSS (383.67 mg/L), oil/fats (502.0 µg/L), phenol (11.0 µg/L), and zinc (21,000 mg/L). IPAL oil WWTP outlet have two parameter sexceeded the quality standars which were oil/fats (313.0 µg/L) and total coliform (> 979 cells/100 mL). The result indicating  that the status of water quality of Digoel River are categorized as “lightly polluted”. Therefore based on utilization, it was categorized as class IV water quality that can be used for irrigating, planting and other purposed that meet the requairement of water qualiy in this class, while for other uses need necessary processing. In order  not to  increase the pollution in the Digoel river the WWTP of industry around Digoel River should improved their treatment, so that waste water discharged to the Digoel River not exceed the stanards quality.Key words: water quality, digoel river, status of water quality, pollutant index