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1. High pO2 Flux Growth and Characterization of NdNiO3 Crystals

   https://doi.org/10.3390/cryst13020180  

   Wang, Xiaoli ; Wang, Shilei ; Liu, Chao ; Fan, Chuanyan ; Han, Lu ; Li, Feiyu ; Chang, Tieyan ; Chen, Yu-Sheng ; Wang, Shanpeng ; Tao, Xutang ; et al ( February 2023 , Crystals)

   Single crystals of the perovskite nickelate NdNiO3 with dimensions of up to 50 μm on edge have been successfully grown using the flux method at a temperature of 400 °C and oxygen pressure of 200 bar. The crystals were investigated by a combination of techniques, including high-resolution synchrotron X-ray single-crystal and powder diffraction and physical property measurements such as magnetic susceptibility and resistivity. Resistivity measurements revealed a metal-insulator transition (MIT) at TMIT~180 K with apparent thermal hysteresis; however, no superlattice peaks or peak splitting below TMIT, which corresponds to a structural transition from Pbnm to P21/n, was observed. The successful growth of NdNiO3 crystals at relatively low temperatures and oxygen pressure provides an alternative approach for preparing single crystals of interesting perovskites such as RNiO3 (R = Sm-Lu) and parent phases of superconducting square planar nickelates.
2. Doping dependent electronic and magnetic ordering in mixed-valent La _1−x Sr _x MnO ₃ thin films

   https://doi.org/10.1088/2053-1591/ac4762  

   Payne, J. A. ; Bryant, C. T. ; Marquez Tavera, R. ; Brown, D. T. ; Pekarek, T. M. ; Warusawithana, M. P. ( January 2022 , Materials Research Express)

   We have investigated the collective electronic and magnetic orderings of a series of La_1−xSr_xMnO₃thin films grown epitaxially strained to (001) oriented strontium titanate substrates as a function of doping,x, for 0 ≤x≤ 0.4. We find that the ground states of these crystalline thin films are, in general, consistent with that observed in bulk crystals and thin film samples synthesized under a multitude of techniques. Our systematic study, however, reveal subtle features in the temperature dependent electronic transport and magnetization measurements, which presumably arise due to Jahn-Teller type distortions in the lattice for particular doping levels. For the parent compound LaMnO₃(x= 0), we report evidence of a strain-induced ferromagnetic ordering in contrast to the antiferromagnetic ground state found in bulk crystals.
3. Measured and simulated thermoelectric properties of FeAs _2−x Se _x ( x = 0.30–1.0): from marcasite to arsenopyrite structure

   https://doi.org/10.1039/d0ma00371a  

   Perez, Christopher J. ; Devlin, Kasey P. ; Skaggs, Callista M. ; Tan, Xiaoyan ; Frank, Corey E. ; Badger, Jackson R. ; Kang, Chang-Jong ; Emge, Thomas J. ; Kauzlarich, Susan M. ; Taufour, Valentin ; et al ( August 2020 , Materials Advances)

   FeAs 2−x Se x ( x = 0.30–1.0) samples were synthesized as phase pure powders by conventional solid-state techniques and as single crystals ( x = 0.50) from chemical vapor transport. The composition of the crystals was determined to be Fe 1.025(3) As 1.55(3) Se 0.42(3) , crystallizing in the marcasite structure type, Pnnm space group. FeAs 2−x Se x (0 < x < 1) was found to undergo a marcasite-to-arsenopyrite ( P 2 1 / c space group) structural phase transition at x ∼ 0.65. The structures are similar, with the marcasite structure best described as a solid solution of As/Se, whereas the arsenopyrite has ordered anion sites. Magnetic susceptibility and thermoelectric property measurements from 300–2 K were performed on single crystals, FeAs 1.50 Se 0.50 . Paramagnetic behavior is observed from 300 to 17 K and a Seebeck coefficient of −33 μV K −1 , an electrical resistivity of 4.07 mΩ cm, and a very low κ l of 0.22 W m −1 K −1 at 300 K are observed. In order to determine the impact of the structural transition on the high-temperature thermoelectric properties, polycrystalline FeAs 2−x Se x ( x = 0.30, 0.75, 0.85, 1.0) samplesmore »were consolidated into dense pellets for measurements of thermoelectric properties. The x = 0.85 sample shows the best thermoelectric performance. The electronic structure of FeAsSe was calculated with DFT and transport properties were approximately modeled above 500 K.« less
4. Single crystal neutron and magnetic measurements of Rb ₂ Mn ₃ (VO ₄ ) ₂ CO ₃ and K ₂ Co ₃ (VO ₄ ) ₂ CO ₃ with mixed honeycomb and triangular magnetic lattices

   https://doi.org/10.1039/C9DT03389K  

   Smith Pellizzeri, Tiffany M. ; Sanjeewa, Liurukara D. ; Pellizzeri, Steven ; McMillen, Colin D. ; Garlea, V. Ovidiu ; Ye, Feng ; Sefat, Athena S. ; Kolis, Joseph W. ( April 2020 , Dalton Transactions)

   Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I , Rb 2 Mn 3 (VO 4 ) 2 CO 3 , crystallizes in the trigonal crystal system in the space group P 3̄1 c , and compound II , K 2 Co 3 (VO 4 ) 2 CO 3 , crystallizes in the hexagonal space group P 6 3 / m . Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO 6 octahedra and MO 5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c -axis through tetrahedral [VO 4 ] groups. The MO 5 units are connected with each other by carbonate groups in the ab -plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO 6more »-honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO 5 triangular lattice ordered below 2.3 K in a colinear ‘up–up–down’ fashion, followed by a planar ‘Y’ type magnetic structure. K 2 Co 3 (VO 4 ) 2 CO 3 ( II ) exhibits a canted antiferromagnetic ordering below T N = 8 K. The Curie–Weiss fit (200–350 K) gives a Curie–Weiss temperature of −42 K suggesting a dominant antiferromagnetic coupling in the Co 2+ magnetic sublattices.« less
5. Tuning the magnetic ground state of Ce1-xYbxRhIn5 by Yb valence fluctuations

   https://doi.org/DOI:10.1103/PhysRevB.98.195118  

   Jang, S. ; Pouse, N. ; Keiber, T. ; White, B. D. ; Disseler, S. M. ; Lynn, J. W. ; J. C. Collini, J. C. ; Janoschek, M. ; Bridges, F. ; Maple, M. B. ( November 2018 , Physical review. B, Condensed matter)

   We characterize the properties of Ce1−xYbxRhIn5 single crystals with 0  x  1 using measurements of powder x-ray diffraction, energy dispersive x-ray spectroscopy, electrical resistivity, magnetic susceptibility, specific heat, x-ray absorption near edge structure (XANES), and neutron diffraction. The Yb valence vYb, calculated from the magnetic susceptibility and measured using XANES, decreases from 3+ at x = 0 to ∼2.1+ at xact = 0.2, where xact is the measured Yb concentration. A transition from incommensurate to commensurate antiferromagnetism is observed in neutron diffraction measurements along Q = (0.5, 0.5, l) between 0.2  xact  0.27; this narrative is supported by specific-heat measurements in which a second robust feature appears at a temperature TI (TI < TN) for the same concentration range. Magnetic susceptibility measurements also reveal features which provide additional evidence of magnetic ordering. The results of this study suggest that the evolution of the Yb valence plays a critical role in tuning the magnetic ground state of Ce1−xYbxRhIn5.