A MnIIIspin crossover complex with atypical two‐step hysteretic thermal switching at 74 K and 84 K shows rich structural–magnetic interplay and magnetic‐field‐induced spin state switching below 14 T with an onset below 5 T. The spin states, structures, and the nature of the phase transitions are elucidated via X‐ray and magnetization measurements. An unusual intermediate phase containing four individual sites, where
A MnIIIspin crossover complex with atypical two‐step hysteretic thermal switching at 74 K and 84 K shows rich structural–magnetic interplay and magnetic‐field‐induced spin state switching below 14 T with an onset below 5 T. The spin states, structures, and the nature of the phase transitions are elucidated via X‐ray and magnetization measurements. An unusual intermediate phase containing four individual sites, where
- NSF-PAR ID:
- 10363273
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie
- Volume:
- 134
- Issue:
- 4
- ISSN:
- 0044-8249
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract are in a pure low spin state, is observed. The splitting of equivalent sites in the high temperature phase into four inequivalent sites is due to a structural reorganization involving a primary and a secondary symmetry‐breaking order parameter that induces a crystal system change from orthorhombic→monoclinic and a cell doubling. Further cooling leads to a reconstructive phase transition and a monoclinic low‐temperature phase with two inequivalent low‐spin sites. The coupling between the order parameters is identified in the framework of Landau theory. -
Abstract CeOs4Sb12, a member of the skutterudite family, has an unusual semimetallic low-temperature
-phase that inhabits a wedge-like area of the fieldH —temperatureT phase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs4Sb12single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the differentH –T phase boundaries. While the high-temperature valence transition between the metallic -phase and the -phase is shifted to higherT by pressures of the order of 1 GPa, we observed only a marginal suppression of the -phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the -phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs4Sb12which appears to be limited to the low-field region. -
Abstract There has been a great deal of recent interest in extended compounds containing Ru3+and Ru4+in light of their range of unusual physical properties. Many of these properties are displayed in compounds with the perovskite and related structures. Here we report an array of structurally diverse hybrid ruthenium halide perovskites and related compounds: MA2Ru
X 6(X =Cl or Br), MA2M RuX6(M =Na, K or Ag;X =Cl or Br) and MA3Ru2X 9(X =Br) based upon the use of methylammonium (MA=CH3NH3+) on the perovskite A site. The compounds MA2RuX 6with Ru4+crystallize in the trigonal space groupand can be described as vacancy‐ordered double‐perovskites. The ordered compounds MA2 M RuX 6with M+and Ru3+crystallize in a structure related to BaNiO3with alternatingMX 6and RuX 6face‐shared octahedra forming linear chains in the trigonalspace group. The compound MA3Ru2Br9crystallizes in the orthorhombic Cmcm space group and displays pairs of face‐sharing octahedra forming isolated Ru2Br9moieties with very short Ru–Ru contacts of 2.789 Å. The structural details, including the role of hydrogen bonding and dimensionality, as well as the optical and magnetic properties of these compounds are described. The magnetic behavior of all three classes of compounds is influenced by spin–orbit coupling and their temperature‐dependent behavior has been compared with the predictions of the appropriate Kotani models. -
Abstract There has been a great deal of recent interest in extended compounds containing Ru3+and Ru4+in light of their range of unusual physical properties. Many of these properties are displayed in compounds with the perovskite and related structures. Here we report an array of structurally diverse hybrid ruthenium halide perovskites and related compounds: MA2Ru
X 6(X =Cl or Br), MA2M RuX6(M =Na, K or Ag;X =Cl or Br) and MA3Ru2X 9(X =Br) based upon the use of methylammonium (MA=CH3NH3+) on the perovskite A site. The compounds MA2RuX 6with Ru4+crystallize in the trigonal space groupand can be described as vacancy‐ordered double‐perovskites. The ordered compounds MA2 M RuX 6with M+and Ru3+crystallize in a structure related to BaNiO3with alternatingMX 6and RuX 6face‐shared octahedra forming linear chains in the trigonalspace group. The compound MA3Ru2Br9crystallizes in the orthorhombic Cmcm space group and displays pairs of face‐sharing octahedra forming isolated Ru2Br9moieties with very short Ru–Ru contacts of 2.789 Å. The structural details, including the role of hydrogen bonding and dimensionality, as well as the optical and magnetic properties of these compounds are described. The magnetic behavior of all three classes of compounds is influenced by spin–orbit coupling and their temperature‐dependent behavior has been compared with the predictions of the appropriate Kotani models. -
Abstract Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking to date. The primary controversy regarding the structure of amorphous
Se relates to the relative fraction of Se atoms residing inchains versus in Se8rings. Herein we present the results of a two‐dimensional solid‐state77Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that 1) the Se8rings and the chains are characterized by their unique77Se NMR signatures and 2) the structure of amorphous Se consists exclusively of chains.