Crystal and Magnetic Structures of High Pressure Perovskite-Type Oxyfluorides,PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 [Pb(Fe0.5Ti0.5)O2.5F0.5]

2006 ◽  
Vol 988 ◽  
Author(s):  
Tetsuhiro Katsumata ◽  
Akihiro Takase ◽  
Masashi Yoshida ◽  
Yoshiyuki Inaguma ◽  
John E. Greedan ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
High Pressures ◽  
Neel Temperature ◽  
X Ray Diffraction ◽  
Néel Temperature ◽  
Magnetic Structures ◽  
Ion Shifts ◽  
A Site ◽  
Perovskite Type ◽  
Crystal And Magnetic Structures

AbstractThe perovskites PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 were synthesized at high temperatures (1000°C) and high pressures (4 – 6 GPa). The crystal and magnetic structures were determined using powder neutron diffraction. Quenched PbFeO2F has the cubic perovskite-type, Pm3m, structure in which the Pb ion shifts from ideal A-site along the <110> directions, which is in good accordance with a previous report. The magnetic structure is antiferromagnetic G-type with propagation vector k = (1/2 1/2 1/2) and an Fe3+ ordered moment of 3.83 μB at 283K. The Néel temperature is 655(5) K. Annealed PbFeO2F has a tetragonal perovskite-type structure at room temperature and transforms reversibly from tetragonal to cubic at approximately 470 K. A superlattice with dimensions a × a × 5c is observed both in electron and x-ray diffraction. The solid solution 0.5PbFeO2F-0.5PbTiO3 belongs to the non-centrosymmetric space group P4mm. The magnetic structure is G-type antiferromagnetic and shows a weak ferromagnetic moment at 4 K. Consequently, 0.5PbFeO2F-0.5PbTiO3 is simultaneously ferroelectric and a weak ferromagnet at low temperature. The Néel temperature is 450 K but the temperature dependence of the ordered Fe moment is anomalous.

Magneto-dielectric anomaly in (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 electroceramic

2014 ◽  
Vol 1636 ◽  
Author(s):  
Shalini Kumari ◽  
Nora Ortega ◽  
Ashok Kumar ◽  
Ram S. Katiyar
Keyword(s):  
Dielectric Response ◽  
Analytical Data ◽  
Rhombohedral Phase ◽  
Dielectric Anomaly ◽  
Neel Temperature ◽  
X Ray Diffraction ◽  
Néel Temperature ◽  
Conventional Solid State Reaction ◽  
Diffraction Patterns ◽  
Small Chemical

ABSTRACTWe report magneto-dielectric anomaly of the multiferroic (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) ceramic near Néel temperature. The ceramic pellets were synthesized by conventional solid state reaction route. X-ray diffraction patterns revealed that most of the peaks shifted slightly towards higher Bragg’s angle compared to those of pure BiFeO3 and also confirmed the formation of rhombohedral phase. It also suggests that the small chemical substitution of Nd and Mn atoms at Bi and Fe sites of BiFeO3 (BFO) perovskite respectively does not alter the crystal structure. Temperature and frequency dependent dielectric response indicate large dielectric anomaly at 620 K, slightly below the known Néel temperature of BFO. The enhancement in dielectric properties of BNFM ceramic was observed as compared to BFO due to suppression of oxygen vacancies by the doping. Temperature dependent dielectric response in conjunction with Raman and thermo-analytical data show that the BNFM sample presents significant magneto-dielectric response around Néel temperture TN ∼ 620 K.

Crystal growth and physical properties of an antiferromagnetic molecule: trans-dibromidotetrakis(acetonitrile)chromium(III) tribromide, [CrBr2(NCCH3)4](Br3)

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Ranuri S. Dissanayaka Mudiyanselage ◽  
Tai Kong ◽  
Weiwei Xie
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Measurements ◽  
Interaction Analysis ◽  
Theoretical Calculations ◽  
Magnetic Feature ◽  
Maximum Temperature ◽  
Neel Temperature ◽  
X Ray Diffraction ◽  
Néel Temperature ◽  
X Ray

The synthesis, crystal structure determination, magnetic properties and bonding interaction analysis of a novel 3d transition-metal complex, [CrBr2(NCCH3)4](Br3), are reported. Single-crystal X-ray diffraction results show that [CrBr2(NCCH3)4](Br3) crystallizes in space group C2/m (No. 12) with a symmetric tribromide anion and the powder X-ray diffraction results show the high purity of the material specimen. X-ray photoelectron studies with a combination of magnetic measurements demonstrate that Cr adopts the 3+ oxidation state. Based on the Curie–Weiss analysis of magnetic susceptibility data, the Néel temperature is found to be around 2.2 K and the effective moment (μeff) of Cr3+ in [CrBr2(NCCH3)4](Br3) is ∼3.8 µB, which agrees with the theoretical value for Cr3+. The direct current magnetic susceptibility of the molecule shows a broad maximum at ∼2.3 K, which is consistent with the theoretical Néel temperature. The maximum temperature, however, shows no clear frequency dependence. Combined with the observed upturn in heat capacity below 2.3 K and the corresponding field dependence, it is speculated that the low-temperature magnetic feature of a broad transition in [CrBr2(NCCH3)4](Br3) could originate from a crossover from high spin to low spin for the split d orbital level low-lying states rather than a short-range ordering solely; this is also supported by the molecular orbital diagram obtained from theoretical calculations.

Magnetic phase separation and strong enhancement of the Néel temperature at high pressures in a new multiferroic Ba3TaFe3Si2O14

JETP Letters ◽  
2017 ◽  
Vol 105 (1) ◽  
pp. 26-33 ◽  
Author(s):  
I. S. Lyubutin ◽  
S. S. Starchikov ◽  
A. G. Gavriliuk ◽  
I. A. Troyan ◽  
Yu. A. Nikiforova ◽  
...  
Keyword(s):  
Phase Separation ◽  
High Pressures ◽  
Magnetic Phase ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Strong Enhancement

scholarly journals Removal of Methyl Violet from Aqueous Solutions Using the A Site Doped Perovskite +-Oxides BaxSr3-xNbO5.5 (x=0, 1 and 2)

2020 ◽  
Vol 3 (1) ◽  
pp. 23-31
Author(s):  
Labib. A. Awin ◽  
Mahmoud. A. El-Rais ◽  
Abdunnaser M Etorki ◽  
Moda. M. Ezrgane
Keyword(s):  
Aqueous Solutions ◽  
Crystal Size ◽  
Methyl Violet ◽  
X Ray Diffraction ◽  
Removal Capacity ◽  
Three Samples ◽  
A Site ◽  
Perovskite Type ◽  
Perovskite Type Structure ◽  
Maximum Removal

Three members of the A- site doped Nb perovskites with general formula Sr3NbO5.5, BaSr2NbO5.5 and Ba2SrNbO5.5 were synthesised by solid-state methods and their removal efficiency of Methyl violet from aqueous solutions investigated. The X-ray diffraction measurements demonstrated that the three samples have a faced cubic perovskite-type structure in space group Fm m. The addition of Ba2+ into the A-site of Sr3NbO5.5 has influenced the cell volume, crystal size and density. Subsequently, the removal capacity was also impacted. The crystallite size of the oxides was determined to be less than 82 nm. The maximum removal capacities of Methyl violet are found to be 46.5, 13.1 and 8.0 mg/g using Ba2SrNbO5.5, BaSr2NbO5.5 and Sr3NbO5.5 respectively. The amounts of the dye adsorbed by the oxides have increased as the Ba2+ content increased. The removals of Methyl violet have positive relationship with pH, temperature and the mass of the oxides.

The magnetic structure of neodymium crystal below the néel temperature

1990 ◽  
Vol 20 (3-4) ◽  
pp. 195-209 ◽  
Author(s):  
A. Jaroszewicz ◽  
P. Kociński ◽  
G. Tecza ◽  
J. Kociński
Keyword(s):  
Magnetic Structure ◽  
Neel Temperature ◽  
Néel Temperature

scholarly journals Crystal and magnetic structures of R 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)

2021 ◽  
Vol 77 (5) ◽  
pp. 824-832
Author(s):  
Stanisław Baran ◽  
Aleksandra Deptuch ◽  
Andreas Hoser ◽  
Bogusław Penc ◽  
Yuriy Tyvanchuk ◽  
...  
Keyword(s):  
Rare Earth ◽  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moments ◽  
Symmetry Analysis ◽  
Crystalline Electric Field ◽  
Magnetic Structures ◽  
Antiferromagnetic Ordering ◽  
Crystal And Magnetic Structures ◽  
The Rare Earth

The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.

scholarly journals Magnetic Structures of Some Multiferroics

2016 ◽  
Vol 1 (1) ◽  
pp. 135
Author(s):  
M.A. Semkin ◽  
N.V. Urusova ◽  
D.G. Kellerman ◽  
A.P. Nosov ◽  
S. Lee ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Magnetic Moment ◽  
Single Phase ◽  
Magnetic Order ◽  
Magnetic Structures ◽  
Propagation Vector ◽  
Ferrimagnetic Structure ◽  
Crystal And Magnetic Structures

<p>We studied crystal and magnetic structures of some composite and single-phase multiferroics: (<em>x</em>)MFe<sub>2</sub>O<sub>4</sub> + (1-<em>x</em>)BaTiO<sub>3</sub>, Ni<sub>3-<em>y</em></sub>Co<em><sub>y</sub></em>V<sub>2</sub>O<sub>8</sub>, and Bi<sub>0.9</sub>Ba<sub>0.1</sub>Fe<sub>0.9</sub>Ti<sub>0.1</sub>O<sub>3</sub>. Composite multiferroics (<em>x</em>)MFe<sub>2</sub>O<sub>4</sub> + (1-<em>x</em>)BaTiO<sub>3</sub> with <em>x</em> = (0.2; 0.3; 0.4) and M = (Ni, Co) have ferrimagnetic structure, which is described by the propagation vector <strong><em>k</em></strong> = 0. Oxides Ni<sub>3-<em>y</em></sub>Co<em><sub>y</sub></em>V<sub>2</sub>O<sub>8</sub> with <em>y</em> = (0.1; 0.3; 0.5) possess a modulated magnetic structure, described by the vector <strong><em>k</em></strong> = (δ, 0, 0), where δ = 0.283 and 0.348 at 7.4 K for <em>y</em> = 0.1 and 0.5, respectively. In the Bi<sub>0.9</sub>Ba<sub>0.1</sub>Fe<sub>0.9</sub>Ti<sub>0.1</sub>O<sub>3</sub> multiferroic a magnetic order is destroyed at 600 K and the Fe-ion magnetic moment decreases from µ = 3.46(5) μ<sub>B</sub> at 300 K to zero at 600 K.</p>

The Nd-Doping Effect on Dielectric Abnormity of BiFeO3 Ceramics below the Néel Temperature

2011 ◽  
Vol 687 ◽  
pp. 439-446 ◽  
Author(s):  
Dong Ge Chen ◽  
Xin Gui Tang ◽  
Qiu Xiang Liu ◽  
Xiao Fang Cheng ◽  
Yan Zou
Keyword(s):  
Complex Impedance ◽  
Precipitation Method ◽  
Neel Temperature ◽  
X Ray Diffraction ◽  
Néel Temperature ◽  
Low Leakage ◽  
Low Leakage Current ◽  
Different Temperatures ◽  
Co Precipitation ◽  
Complex Impedance Spectra

Bismuth neodymium ferrite (Bi1-xNdxFeO3: BNFO;x=0, 0.025, 0.075, 0.125, 0.175) ceramics were prepared by a co-precipitation method and sintered at 800 °C, using nitrates as precursors. The crystal structure and dielectric properties of the samples were characterized by X-ray diffraction （XRD）and dielectric permittivity measurement at different temperatures and frequencies. XRD suggests that the impurity phases are weakened by suitably dopingx=0.075. Dielectric spectra indicate that relaxation peaks below the Néel temperature which may be produced by the effect of grain boundaries and dipoles with heating vanish after doping Nd at the same content. Complex impedance spectra manifest that the doped samples are closer to Debye-type, and the impedance rises which will lead to low leakage current.

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