Conduction Characteristics of Charge Ordering Type Ferroelectrics,YFe2O4

2006 ◽  
Vol 966 ◽  
Author(s):  
Ken Imamura ◽  
Yoichi Horibe ◽  
Takeshi Yoshimura ◽  
Norifumi Fujimura ◽  
Shigeo Mori ◽  
...  
Keyword(s):  
Room Temperature ◽  
Inflection Point ◽  
Oxygen Deficiency ◽  
Complex Impedance ◽  
Charge Ordering ◽  
Neel Temperature ◽  
Ohmic Conduction ◽  
Néel Temperature ◽  
Impedance Measurements ◽  
Conduction Properties

ABSTRACTElectrical conduction properties of charge ordering type ferroelectrics YFe2O4 were investigated. YFe2O4 was synthesized in reduced atmosphere at 1200 °C. Oxygen partial pressure of the reduced atmosphere was controlled by the equilibrium state of CO and CO2. YFe2O4 is paramagnetic at room temperature and has Néel temperature around 250K. The Néel temperature was decreased with increasing the amount of oxygen deficiency. Moreover, YFe2O4 showed ohmic conduction from 260 to 100 K. The temperature dependence of the DC conductivity showed an inflection point at the Néel temperature, which indicated the development of charge ordering of Fe2+ and Fe3+ ions. From the complex impedance measurements, the equivalent circuits of YFe2O4 with different oxygen deficiency were determined at various temperatures.

Oxygen deficiency-induced anomalous enhancement of Neel temperature and magnetic coupling for Bi0.9Ca0.1FeO3−δ and Bi0.9Pb0.1FeO3−δ

2016 ◽  
Vol 111 ◽  
pp. 297-304 ◽  
Author(s):  
Hsiung Chou ◽  
Chen-Wei Yen ◽  
Chun-Chuen Yang ◽  
G.D. Dwivedi ◽  
Kung Shuang Yang ◽  
...  
Keyword(s):  
Oxygen Deficiency ◽  
Magnetic Coupling ◽  
Neel Temperature ◽  
Néel Temperature

Two-dimensional C12Mn2/C12Cr2 as a room-temperature half metal/antiferromagnetic semiconductor: a systematic study

2017 ◽  
Vol 19 (4) ◽  
pp. 3394-3404 ◽  
Author(s):  
Zheng-Zhe Lin
Keyword(s):  
Systematic Study ◽  
Room Temperature ◽  
Neel Temperature ◽  
Two Dimensional ◽  
Néel Temperature ◽  
Half Metal

Two-dimensional C12Mn2/C12Cr2 as a half metal/antiferromagnetic semiconductor with high Curie/Néel temperature.

STUDY OF NÉEL TEMPERATURE AND MULTIPLE PHASE COEXISTENCE IN Bi0.5Ca0.5-xBaxMnO3 (x = 0–0.10)

2012 ◽  
Vol 26 (08) ◽  
pp. 1250049
Author(s):  
RENWEN LI ◽  
LI PI ◽  
WEI TONG ◽  
LEI ZHANG ◽  
LANGSHENG LING ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Charge Ordering ◽  
Magnetic Data ◽  
Perovskite Manganites ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Multiple Phase ◽  
Magnetic Analysis ◽  
Structural And Magnetic Properties ◽  
Lower Temperature

Structural and magnetic properties of Bi0.5 Ca0.5-xBaxMnO3 (x = 0, 0.03, 0.05, 0.07 and 0.10) samples with charge ordering (CO) state and C-type antiferromagnetic (AFM) magnetic structure have been studied systematically. With increasing Ba-doping level, both CO and AFM are weakened. From the micro-magnetic analysis, we clarify the ambiguity about the Néel temperature TN in bismuth-based perovskite manganites. We find that the paramagnetic (PM)-CO/AFM transition temperature TCO at high temperature is the onset temperature of the PM–AFM transition, while customarily so-called TN at low temperature indicates the finish of the PM–AFM transition. Both the macro- and micro-magnetic data show that, in all the samples, only AFM state coexists with PM matrix below CO transition and above TN, while AFM state coexists with ferromagnetic (FM) state and PM state at lower temperature below TN.

Lithium Insertion in La2NiO4+y

1990 ◽  
Vol 210 ◽  
Author(s):  
A. Várez ◽  
U. Amador ◽  
E. Morán ◽  
M.A. Alario-Franco
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Complex Impedance ◽  
Ionic Conductor ◽  
Lithium Insertion ◽  
Orthorhombic Structure ◽  
Soft Chemistry ◽  
Impedance Measurements ◽  
Temperature Range

AbstractA series of lithium inserted La2NiO4+y has been prepared by the soft chemistry route with n-butyllithium at room temperature.The insertion leads to a lowering in symmetry, from the tetragonal K2NiF4 type to an orthorhombic structure.Neutron diffraction experiments show that as in stoichiometric La2NiO4.00 the inserted material is antiferromagnetic.Complex impedance measurements indicate it to be an ionic conductor in the temperature range extending from 60 to 300°C.

scholarly journals Deformations of the α-Fe2O3 rhombohedral lattice across the Néel temperature

2017 ◽  
Vol 73 (1) ◽  
pp. 27-32 ◽  
Author(s):  
P. Fabrykiewicz ◽  
M. Stękiel ◽  
I. Sosnowska ◽  
R. Przeniosło
Keyword(s):  
Room Temperature ◽  
Chem Phys ◽  
Nanowire Growth ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Monoclinic Symmetry ◽  
Model Calculations ◽  
Peak Broadening ◽  
Monoclinic Lattice ◽  
Diffraction Patterns

High-resolution synchrotron radiation powder diffraction patterns of α-Fe2O3 measured between room temperature and 1100 K, i.e. above the Néel temperature T N = 950 K, have been analyzed. The integral breadths of the Bragg peaks show a hkl-dependent anisotropy, both below and above T N. This anisotropy can be quantitatively described by using a statistical peak-broadening model [Stephens (1999). J. Appl. Cryst. 32, 281]. Model calculations show that the rhombohedral α-Fe2O3 lattice is deformed and the deformation leads to a monoclinic lattice with the unique monoclinic axis along the hexagonal [110] direction both below and above T N. The monoclinic symmetry of bulk α-Fe2O3 is compatible with α-Fe2O3 nanowire growth along the [110] direction reported in Fu et al. [Chem. Phys. Lett. (2001), 350, 491].

Giant Magnetothermopower in Sm0.55Sr0.45MnO3 Manganite

2015 ◽  
Vol 233-234 ◽  
pp. 141-144
Author(s):  
Liudmila I. Koroleva ◽  
Artiom S. Morozov ◽  
E.S. Zhakina
Keyword(s):  
Magnetic Field ◽  
Curie Temperature ◽  
Temperature Dependence ◽  
Charge Ordering ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Oxygen Ions ◽  
Sharp Minimum ◽  
Large Maximum ◽  
A Charge

Thermopower α and magnetothermopower ∆α/α were studied in the Sm0.55Sr0.45MnO3 samples, containing clusters of three types: ferromagnetic clusters with the Curie temperature TC = 126 K, A-type antiferromagnetic clusters with the Neel temperature TNA ≥ TC and CE-type antiferromagnetic clusters with the TNCE = 240 K. The curves of temperature dependence of α (T) have a large maximum including TC and TNCE and the sharp minimum on the {∆α/α}(T) curves in the TC-region. Negative magnetothermopower in minimum achieves the giant value ~ 85% in magnetic field 14.17 kOe. It is shown that thermopower is largely caused by the presence of ferromagnetic nanoclusters of ferron-type and to a lesser degree of CE-type antiferromagnetic clusters, in which there is a charge ordering, displacing oxygen ions.

STRUCTURAL ANALYSIS AND IONIC CONDUCTIVITY AT ROOM TEMPERATURE OF A Ce-DOPED La0.9MnO3-δ PEROVSKITE PREPARED BY THE PECHINI ROUTE

2009 ◽  
Vol 02 (01) ◽  
pp. 33-36
Author(s):  
FARIDA BOUREMMAD ◽  
ABDERRAHIM BENABBAS ◽  
NEDJMEDDINE BOUNAR ◽  
KAMEL RIDA ◽  
PATRICK ROPA ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Ionic Conductivity ◽  
Ethylene Glycol ◽  
Room Temperature ◽  
Perovskite Phase ◽  
Oxygen Deficiency ◽  
Complex Impedance ◽  
Solid Oxide ◽  
X Ray Diffraction ◽  
X Ray

A Ce -doped La 0.9 MnO 3-δ sample was prepared by the Pechini route, consisting of a polymerization of citric acid and ethylene glycol, in order to prepare a phase with oxygen deficiency that can be used in fuel cell applications. To substitute a part of lanthanum by cerium, we added CeO 2 in excess to force it to react and diffuse in the perovskite. The Fourier Transformed infrared (FTIR) spectrum of the resin at 200°C has shown the formation of complex metals form and polymerized form of ethylene glycol. The X-ray diffraction (XRD) spectrum of the sample, calcined at 900°C, has revealed that the sample is mainly constituted by a deficient rhombohedra perovskite phase. The measurement of the ionic conductivity by complex impedance at room temperature has given a relatively high value, which opens up an opportunity for solid oxide fuel cell applications.

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.

scholarly journals Sintering Temperature Dependent Permeability of Nanocrystalline Ni0.20Cu0.30Zn0.50Fe2O4 Ferrite

2011 ◽  
Vol 35 (1) ◽  
pp. 67-75 ◽  
Author(s):  
ML Rahman ◽  
MHR Khan ◽  
ST Mahmud ◽  
AKM Akther Hossain
Keyword(s):  
Room Temperature ◽  
Sintering Temperature ◽  
Spinel Ferrite ◽  
Magnetization Measurement ◽  
Initial Permeability ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Dc Magnetization ◽  
Average Grain Size ◽  
Auto Combustion

The spinel ferrite of Ni0.20Cu0.30Zn0.50Fe2O4 was studied at room temperature using X-ray diffraction pattern prepared by auto combustion technique. The analysis of the XRD patterns showed that the sample has a single phase cubic spinel structure. The bulk density, average grain size and initial permeability increase with increasing sintering temperature up to a optimum temperature. Beyond that temperature all those properties decreases. The value of relative quality factor decreases with increasing sintering temperature. The DC magnetization measurement showed that at room temperature the sample is in ferrimagnetic state. The number of Bohr magneton, n(?B), Néel temperature, TN, and the field at which saturation occurs were also calculated and possible explanation for the observed characteristics of microstructure, initial permeability, DC magnetization, and Néel temperature of the studied sample are presented.DOI: http://dx.doi.org/10.3329/jbas.v35i1.7972Journal of Bangladesh Academy of Sciences, Vol.35, No.1, 67-75, 2011

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