scholarly journals Ferromagnetic ordering in La0.7Sr0.3Mn3+0.85Nb5+0.15O3 manganite

2015 ◽  
Vol 30 (S1) ◽  
pp. S97-S100 ◽  
Author(s):  
I. O. Troyanchuk ◽  
M. V. Bushinsky ◽  
V. Efimov ◽  
S. Schorr ◽  
C. Ritter ◽  
...  
Keyword(s):  
Curie Point ◽  
Room Temperature ◽  
Structural Transition ◽  
Steric Effect ◽  
Structural Parameters ◽  
Orthorhombic Phase ◽  
Structural Disorder ◽  
Orthorhombic Symmetry ◽  
Positive Part ◽  
Ferromagnetic Ordering

Structural measurements have been performed on the La0.7Sr0.3Mn3+0.85Nb5+0.15O3 compound with oxidation state of manganese close to +3. The composition undergoes a structural transition from rhombohedral to orthorhombic symmetry below room temperature. The calculated structural parameters show that the orthorhombic phase is not long-range orbitally ordered and that the structural transition is associated with a steric effect. The compound is ferromagnetic with a Curie point of around 150 K and a magnetic moment of 3.1 μB/Mn. It is suggested that ferromagnetism is originated from superexchange interactions via oxygen. Covalence enhances the positive part of the superexchange interactions whereas structural disorder leads to suppression of ferromagnetism.

scholarly journals Ba5(IO6)2: crystal structure evolution from room temperature to 80 K

2021 ◽  
Vol 77 (6) ◽  
pp. 634-637
Author(s):  
David Wenhua Bi ◽  
Priya Ranjan Baral ◽  
Arnaud Magrez
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Structural Transition ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
Lattice Contraction ◽  
Interatomic Distances ◽  
Crystallographic Axes

The crystal structure of Ba5(IO6)2, pentabarium bis(orthoperiodate), has been re-investigated at room temperature based on single-crystal X-ray diffraction data. In comparison with a previous crystal structure determination by the Rietveld method, an improved precision of the structural parameters was achieved. Additionally, low-temperature measurements allowed the crystal structure evolution to be studied down to 80 K. No evidence of structural transition was found even at the lowest temperature. Upon cooling, the lattice contraction is more pronounced along the b axis. This contraction is found to be inhomogeneous along different crystallographic axes. The interatomic distances between different Ba atoms reduce drastically with lowering temperature, resulting in a closer packing around the IO6 octahedra, which remain largely unaffected.

Structural transition in KMnCrF6 – a chemically ordered magnetic ferroelectric

2015 ◽  
Vol 3 (17) ◽  
pp. 4321-4332 ◽  
Author(s):  
Christina Drathen ◽  
Takeshi Nakagawa ◽  
Wilson A. Crichton ◽  
Adrian H. Hill ◽  
Yasuo Ohishi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Structural Transition ◽  
Tungsten Bronze ◽  
Orthorhombic Phase ◽  
Multiferroic Material ◽  
Tetragonal Tungsten Bronze

Emergence of an orthorhombic phase at room temperature suggests this tetragonal tungsten bronze fluoride to be a potential multiferroic material.

Room-temperature ferroelasticity and unusual sequence of phase transitions in the crystal of (N2H5)3[CdCl5]

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Monika K. Krawczyk ◽  
Zbigniew Czapla ◽  
Adam Ingram ◽  
Andrzej Kozdraś ◽  
Tadeusz Lis ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Structural Changes ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Orthorhombic Symmetry ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cl Atoms

On the basis of thermal analysis (DSC, DTA, DTG), single crystal X-ray diffraction experiments, dielectric studies and optical observation, it is found that the (N2H5)3[CdCl5] crystal exhibits several structural phase transitions. At room temperature, the studied crystal exhibits ferroelastic properties and undergoes phase transition from the monoclinic to the orthorhombic phase on heating above 327 K. Upon subsequent cooling, two structural phase transitions at about 323 and 319 K are observed, where the crystal adopts orthorhombic symmetry. The presented phase transitions are unique due to the fact the first heating run results in different structural changes compared to those observed during cooling and subsequent heating/cooling runs. In the studied crystal, N2H5 + ions and 1D chains built up from {CdCl5}3− units bridged by Cl atoms occur. The phase transitions observed can be associated with reorientation of cations and partial disorder of cations as well as Cl atoms.

scholarly journals Origin of forbidden reflections in multiferroic Ba2CoGe2O7 by neutron diffraction: symmetry lowering or Renninger effect?

2016 ◽  
Vol 49 (2) ◽  
pp. 556-560 ◽  
Author(s):  
Andrew Sazonov ◽  
Martin Meven ◽  
Georg Roth ◽  
Robert Georgii ◽  
István Kézsmárki ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Structural Model ◽  
Structural Parameters ◽  
Theoretical Description ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
X Ray ◽  
Precise Knowledge

For a symmetry-consistent theoretical description of the multiferroic phase of Ba2CoGe2O7 a precise knowledge of its crystal structure is a prerequisite. In a previous synchrotron X-ray diffraction experiment on multiferroic Ba2CoGe2O7 at room temperature, forbidden reflections were found that favour the tetragonal-to-orthorhombic symmetry lowering of the compound [Hutanu, Sazonov, Murakawa, Tokura, Náfrádi & Chernyshov (2011), Phys. Rev. B, 84, 212101]. Here, the results are reported of room-temperature single-crystal diffraction studies with both hot and cold neutrons to differentiate between genuine symmetry lowering and multiple diffraction (the Renninger effect). A comparison of the experimental multiple diffraction patterns with simulated ones rules out symmetry lowering. Thus, the structural model based on the tetragonal space group P\overline{4}2_{1}m was selected to describe the Ba2CoGe2O7 symmetry at room temperature. The precise structural parameters from neutron diffraction at 300 K are presented and compared with the previous X-ray diffraction results.

scholarly journals Old Donors for New Molecular Conductors: Combining TMTSF and BEDT-TTF with Anionic (TaF6)1−x/(PF6)x Alloys

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 386
Author(s):  
Magali Allain ◽  
Cécile Mézière ◽  
Pascale Auban-Senzier ◽  
Narcis Avarvari
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Density Wave ◽  
Spin Density Wave ◽  
Orthorhombic Phase ◽  
Molecular Conductors ◽  
Bechgaard Salts ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Resistivity Measurements

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors.

scholarly journals Anion ordering enables fast H− conduction at low temperatures

2021 ◽  
Vol 7 (23) ◽  
pp. eabf7883
Author(s):  
Hiroki Ubukata ◽  
Fumitaka Takeiri ◽  
Kazuki Shitara ◽  
Cédric Tassel ◽  
Takashi Saito ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Room Temperature ◽  
Structural Transition ◽  
Hexagonal Lattice ◽  
Ionic Conductors ◽  
Activation Barriers ◽  
Energy Devices ◽  
Energy Applications ◽  
Chemical Disorder ◽  
New Energy

The introduction of chemical disorder by substitutional chemistry into ionic conductors is the most commonly used strategy to stabilize high-symmetric phases while maintaining ionic conductivity at lower temperatures. In recent years, hydride materials have received much attention owing to their potential for new energy applications, but there remains room for development in ionic conductivity below 300°C. Here, we show that layered anion-ordered Ba2−δH3−2δX (X = Cl, Br, and I) exhibit a remarkable conductivity, reaching 1 mS cm−1 at 200°C, with low activation barriers allowing H− conduction even at room temperature. In contrast to structurally related BaH2 (i.e., Ba2H4), the layered anion order in Ba2−δH3−2δX, along with Schottky defects, likely suppresses a structural transition, rather than the traditional chemical disorder, while retaining a highly symmetric hexagonal lattice. This discovery could open a new direction in electrochemical use of hydrogen in synthetic processes and energy devices.

Observation of high ferromagnetic ordering in Fe implanted ZnO at room temperature

2009 ◽  
Vol 267 (10) ◽  
pp. 1783-1786 ◽  
Author(s):  
D. Sanyal ◽  
Mahuya Chakrabarti ◽  
Vaishali Naik ◽  
Tapatee Kundu Roy ◽  
Debasis Bhowmick ◽  
...  
Keyword(s):  
Room Temperature ◽  
Ferromagnetic Ordering

Unraveling the structural transition mechanism of room-temperature compressed graphite carbon

2021 ◽  
Vol 23 (36) ◽  
pp. 20560-20566
Author(s):  
Sheng-cai Zhu ◽  
Qing-yang Hu
Keyword(s):  
High Pressure ◽  
Crystal Orientation ◽  
Room Temperature ◽  
Structural Transition ◽  
Local Strain ◽  
Transition Mechanism

We resolve the transition pathway of compressed graphite, whose complex high-pressure structure is formed by shearing the boat architecture without nuclei core and controlled by local strain and crystal orientation.

Structural and magnetic properties of nitrided finemet-type ribbons

2000 ◽  
Vol 77 (9) ◽  
pp. 731-736
Author(s):  
H Atmani ◽  
S Grognet ◽  
J Teillet ◽  
K Zellama ◽  
R Zuberek
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Crystalline Phase ◽  
Room Temperature ◽  
Structural Parameters ◽  
Thermochemical Treatment ◽  
Specific Magnetization ◽  
Nano Structure ◽  
Magnetostriction Constant ◽  
Structural And Magnetic Properties

Nitriding thermochemical treatment under suitable parameters is used to nano-crystallize Fe73.5Cu1Nb3Si13.5B9 ribbon. This new kind of treatment leads to finer nano-structure and modifies the structural parameters of the α-Fe(Si) phase, obtained during the treatment. The magnetic properties are also improved; specific magnetization at room temperature and Curie temperature of the crystalline phase increase, and the magnetostriction constant becomes smaller. The nitrogenation seems to offer a new way to obtain nanostructured ribbons. PACS No.: 75.70

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