scholarly journals Low-T magnetic anomaly in Ca2Fe2O5studied by single-crystal neutron diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1352-C1352
Author(s):  
Josie Auckett ◽  
Garry McIntyre ◽  
Maxim Avdeev ◽  
Hank De Bruyn ◽  
Chris Ling
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Temperature Interval ◽  
Diffraction Data ◽  
Room Temperature ◽  
Statistical Significance ◽  
Spin Reorientation ◽  
Careful Examination ◽  
Zero Field ◽  
Zone Method

Ca2Fe2O5, which belongs to the Brownmillerite family of promising solid-oxide fuel cell membrane materials, is an antiferromagnet (AFM) below TN = 720 K. A small ferromagnetic (FM) canting perpendicular to the AFM easy axis has previously been established by physical properties measurements, but never observed crystallographically. More intriguingly, it has been known for some time to display an anomalous elevation in magnetic susceptibility for 60 K < T < 140 K. [1] Based on measurements performed with small oriented single crystals, Zhou et al. [2] proposed that this anomaly was due to a reorientation of the spins from the crystallographic a axis to the c axis below 40 K, with a region of minimal magnetocrystalline anisotropy in the anomalous temperature interval. In order to test this, we grew a very large (~1 cm3) single crystal by the floating-zone method and collected neutron Laue diffraction data, against which we refined both the atomic and magnetic structures of Ca2Fe2O5 between 10 K and 300 K. We designed and built an ad hoc sample mount to apply a small (~35 Oe) magnetic field to the sample, ensuring perfect consistency with the magnetic susceptibility data, which were collected in a comparably small field. Our refinements against both zero-field and in-field diffraction data reproduce the G-type AFM structure of Ca2Fe2O5 excellently at room temperature, including the FM canting which we have refined to statistical significance for the first time. We can also show that in the intermediate temperature interval (T = 100 K), the spins are slightly less well-ordered due to competing sublattice interactions. However, careful examination of the data reveals that the material is still best described by the room-temperature magnetic structure at all measured temperatures – i.e., the spin-reorientation hypothesis is incorrect.

scholarly journals The caesium phosphates Cs3(H1.5PO4)2(H2O)2, Cs3(H1.5PO4)2, Cs4P2O7(H2O)4, and CsPO3

2020 ◽  
Vol 151 (9) ◽  
pp. 1317-1328
Author(s):  
Matthias Weil ◽  
Berthold Stöger
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Single Crystal ◽  
Diffraction Data ◽  
Room Temperature ◽  
Structure Type ◽  
Solid State Reactions ◽  
X Ray Diffraction ◽  
Hydrogen Phosphate ◽  
X Ray

Abstract The caesium phosphates Cs3(H1.5PO4)2(H2O)2 and Cs3(H1.5PO4)2 were obtained from aqueous solutions, and Cs4P2O7(H2O)4 and CsPO3 from solid state reactions, respectively. Cs3(H1.5PO4)2, Cs4P2O7(H2O)4, and CsPO3 were fully structurally characterized for the first time on basis of single-crystal X-ray diffraction data recorded at − 173 °C. Monoclinic Cs3(H1.5PO4)2 (Z = 2, C2/m) represents a new structure type and comprises hydrogen phosphate groups involved in the formation of a strong non-symmetrical hydrogen bond (accompanied by a disordered H atom over a twofold rotation axis) and a very strong symmetric hydrogen bond (with the H atom situated on an inversion centre) with symmetry-related neighbouring anions. Triclinic Cs4P2O7(H2O)4 (Z = 2, P$$\bar{1}$$ 1 ¯ ) crystallizes also in a new structure type and is represented by a diphosphate group with a P–O–P bridging angle of 128.5°. Although H atoms of the water molecules were not modelled, O···O distances point to hydrogen bonds of medium strengths in the crystal structure. CsPO3 is monoclinic (Z = 4, P21/n) and belongs to the family of catena-polyphosphates (MPO3)n with a repetition period of 2. It is isotypic with the room-temperature modification of RbPO3. The crystal structure of Cs3(H1.5PO4)2(H2O)2 was re-evaluated on the basis of single-crystal X-ray diffraction data at − 173 °C, revealing that two adjacent hydrogen phosphate anions are connected by a very strong and non-symmetrical hydrogen bond, in contrast to the previously described symmetrical bonding situation derived from room temperature X-ray diffraction data. In the four title crystal structures, coordination numbers of the caesium cations range from 7 to 12. Graphic abstract

Description of Ba1 + x Ni x Rh1 − x O3 with x = 0.1170 (5) in superspace: modulated composite versus modulated-layer structure

2006 ◽  
Vol 62 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Andreas Schönleber ◽  
F. Javier Zúñiga ◽  
J. Manuel Perez-Mato ◽  
Jacques Darriet ◽  
Hans-Conrad zur Loye
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Room Temperature ◽  
Layer Structure ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray

The structure of the compound Ba1 + x Ni x Rh1 − x O3 [x = 0.1170 (5)] has been analyzed at room temperature within the (3 + 1)-dimensional superspace approach using single-crystal X-ray diffraction data. Two different models are presented, the compound is refined as modulated composite as well as modulated-layer structure. In both models discontinuous atomic domains are applied to describe the structural modulations. While the first approach stresses the pseudo-one-dimensional constitution, the latter highlights the layered character of these structures.

The crystal structure of a simple enol formed in a single-crystal-to-single-crystal enolene rearrangement

2004 ◽  
Vol 82 (2) ◽  
pp. 301-305 ◽  
Author(s):  
Kenneth CW Chong ◽  
Brian O Patrick ◽  
John R Scheffer
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Room Temperature ◽  
Thermal Reaction ◽  
Thermal Rearrangement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phenyl Ketone

When crystals of 9-tricyclo[4.4.1.0]undecalyl-4-(carbomethoxy)phenyl ketone (1) were allowed to stand in the dark for extended periods of time at room temperature, the compound underwent a thermal reaction — the enolene rearrangement — to afford enol 2. The crystals remained transparent and appeared unchanged in shape as the reaction proceeded. X-ray diffraction data were collected on single crystals containing 17%, 25%, 66%, and 100% of the enol. The crystal structure of a simple enol was obtained via this novel single-crystal-to-single-crystal enolene rearrangement.Key words: single crystal, thermal, rearrangement, enol, enolene.

High-pressure syntheses and crystal structures of orthorhombic DyGaO3 and trigonal GaBO3

2015 ◽  
Vol 70 (4) ◽  
pp. 207-214 ◽  
Author(s):  
Daniela Vitzthum ◽  
Stefanie A. Hering ◽  
Lukas Perfler ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
High Pressure High Temperature

AbstractOrthorhombic dysprosium orthogallate DyGaO3 and trigonal gallium orthoborate GaBO3 were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 8.5 GPa/1350 °C and 8 GPa/700 °C, respectively. Both crystal structures could be determined by single-crystal X-ray diffraction data collected at room temperature. The orthorhombic dysprosium orthogallate crystallizes in the space group Pnma (Z = 4) with the parameters a = 552.6(2), b = 754.5(2), c = 527.7(2) pm, V = 0.22002(8) nm3, R1 = 0.0309, and wR2 = 0.0662 (all data) and the trigonal compound GaBO3 in the space group R3̅c (Z = 6) with the parameters a = 457.10(6), c = 1419.2(3) pm, V = 0.25681(7) nm3, R1 = 0.0147, and wR2 = 0.0356 (all data).

Refinement of the Ferri- and Paramagnetic Phases of Magnetite from Neutron Multiple Diffraction Data

1998 ◽  
Vol 31 (5) ◽  
pp. 718-725 ◽  
Author(s):  
V. L. Mazzocchi ◽  
C. B. R. Parente
Keyword(s):  
Computer Program ◽  
Single Crystal ◽  
Diffraction Data ◽  
Room Temperature ◽  
Structural Parameters ◽  
Thermal Parameters ◽  
Multiple Diffraction ◽  
Shift Method ◽  
Step Process ◽  
Diffraction Patterns

Structural parameters for the ferrimagnetic and paramagnetic phases of magnetite have been refined from neutron multiple diffraction data. Experimental neutron multiple diffraction patterns were obtained by measuring the 111 primary reflection of a natural single crystal of this compound. Measurements were made at room temperature for the ferrimagnetic phase and at 976 K for the paramagnetic phase. The corresponding simulated patterns have been calculated byMULTI, a computer program for the simulation of neutron multiple diffraction patterns. A step-by-step process was used in the refinements according to the parameter-shift method. Both isotropic and anisotropic thermal parameters were assumed for the temperature factor. Isotropic thermal parameters were considered in two different ways: an overall parameter for all ions in the structure and three different parameters for the three special positions occupied by them in the structure. The best results were found in the refinements with anisotropic thermal parameters. In this case, the values of the profileRfactor found for these refinements were 3.00 and 3.32%, respectively, for the ferrimagnetic and paramagnetic phases.

scholarly journals Investigation of Elastic Properties of the Single-Crystal Nickel-Base Superalloy CMSX-4 in the Temperature Interval between Room Temperature and 1300 °C

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 152
Author(s):  
Alexander Epishin ◽  
Bernard Fedelich ◽  
Monika Finn ◽  
Georgia Künecke ◽  
Birgit Rehmer ◽  
...  
Keyword(s):  
Single Crystal ◽  
Elastic Properties ◽  
Temperature Interval ◽  
Elastic Constants ◽  
Gas Turbines ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Resonance Frequencies ◽  
Nickel Base ◽  
Base Superalloy

The elastic properties of the single-crystal nickel-base superalloy CMSX-4 used as a blade material in gas turbines were investigated by the sonic resonance method in the temperature interval between room temperature and 1300 °C. Elastic constants at such high temperatures are needed to model the mechanical behavior of blade material during manufacturing (hot isostatic pressing) as well as during technical accidents which may happen in service (overheating). High reliability of the results was achieved using specimens of different crystallographic orientations, exciting various vibration modes as well as precise measurement of the material density and thermal expansion required for modeling the resonance frequencies by finite element method. Combining the results measured in this work and literature data the elastic constants of the γ- and γ′-phases were predicted. This prediction was supported by measurement of the temperature dependence of the γ′-fraction. All data obtained in this work are given in numerical or analytical forms and can be easily used for different scientific and engineering calculations.

Inversion parameter of the CoGa2O4 spinel determined from single-crystal X-ray data

2006 ◽  
Vol 62 (5) ◽  
pp. i109-i111 ◽  
Author(s):  
Akihiko Nakatsuka ◽  
Yuya Ikeda ◽  
Noriaki Nakayama ◽  
Tadato Mizota
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Spinel Structure ◽  
Room Temperature ◽  
Structural Formula ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Sites ◽  
Normal Spinel

Single crystals of cobalt digallium tetraoxide, CoGa2O4, have been grown by cooling slowly a 1:1 mixture of CoO and Ga2O3 from 1473 K to room temperature under the presence of a PbF2 flux. The compound crystallizes with the cubic spinel structure (space group Fd\overline{3}m). The occupancy refinement based on single-crystal X-ray diffraction data shows CoGa2O4 to be a largely normal spinel with an inversion parameter of 0.575 (4), resulting in a structural formula of IV(Co0.425Ga0.575)VI[Co0.575Ga1.425]O4, where IV() and VI[] represent the tetrahedral and the octahedral sites, respectively.

NEW MAGNETIC BEHAVIOR OF LaCoO3 SINGLE CRYSTAL AT LOW TEMPERATURE

2010 ◽  
Vol 24 (29) ◽  
pp. 2855-2860 ◽  
Author(s):  
GENG-XIN SONG ◽  
LIANG LI ◽  
DA-PENG XU
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Magnetic Measurements ◽  
Magnetic Behavior ◽  
Wave Crest ◽  
Floating Zone ◽  
Linear Variation ◽  
Zone Method ◽  
Floating Zone Method ◽  
Slope Change

The LaCoO 3 single crystal, 4 mm in diameter and 30 mm in length, has been grown by optical floating zone method. The magnetic measurements show that the coercivity and the remanence are 5 Oe and 1.5 × 10-3 emu/g at 5 K, respectively. The ZFC and FC magnetic susceptibility curves overlap and the 1/χ(T) curve shows a linear variation over the interval 5 K < T < 35 K in 1000 Oe. As the temperature increases from 35 K to 90 K, the ZFC curve in 1000 Oe firstly reduces nonlinearly, and then appears as a wave crest. The χ under ZFC is higher than that under FC in the temperature range of 55~90 K. In 50 000 Oe, a slope change of 1/χ(T) at about 12 K is observed.

scholarly journals NewM+,M3+-arsenates – the framework structures of AgM3+(HAsO4)2(M3+= Al, Ga) andM+GaAs2O7(M+= Na, Ag)

2017 ◽  
Vol 73 (5) ◽  
pp. 785-790 ◽  
Author(s):  
Karolina Schwendtner ◽  
Uwe Kolitsch
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystal ◽  
Diffraction Data ◽  
Room Temperature ◽  
Three Dimensional ◽  
Structure Type ◽  
X Ray Diffraction ◽  
X Ray ◽  
Donor Acceptor ◽  
Anionic Framework

The crystal structures of hydrothermally synthesized silver(I) aluminium bis[hydrogen arsenate(V)], AgAl(HAsO4)2, silver(I) gallium bis[hydrogen arsenate(V)], AgGa(HAsO4)2, silver gallium diarsenate(V), AgGaAs2O7, and sodium gallium diarsenate(V), NaGaAs2O7, were determined from single-crystal X-ray diffraction data collected at room temperature. The first two compounds are representatives of the MCV-3 structure type known for KSc(HAsO4)2, which is characterized by a three-dimensional anionic framework of corner-sharing alternatingM3+O6octahedra (M= Al, Ga) and singly protonated AsO4tetrahedra. Intersecting channels parallel to [101] and [110] host the Ag+cations, which are positionally disordered in the Ga compound, but not in the Al compound. The hydrogen bonds are relatively strong, with O...O donor–acceptor distances of 2.6262 (17) and 2.6240 (19) Å for the Al and Ga compounds, respectively. The two diarsenate compounds are representatives of the NaAlAs2O7structure type, characterized by an anionic framework topology built ofM3+O6octahedra (M= Al, Ga) sharing corners with diarsenate groups, andM+cations (M= Ag) hosted in the voids of the framework. Both structures are characterized by a staggered conformation of the As2O7groups.

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