scholarly journals Structural, Electrical and Magnetic Study in Nanocrystallite La2CuMnO6 Ceramics

2021 ◽  
Author(s):  
Digvijoy Narayan Singh ◽  
S Majumder ◽  
Anupam Mishra ◽  
S Saha ◽  
M Mahato ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Single Phase ◽  
Small Polaron ◽  
Magnetic Behaviour ◽  
Dielectric Dispersion ◽  
X Ray ◽  
Thermally Activated ◽  
X Ray Absorption ◽  
Nano Size ◽  
Super Exchange Interaction

Abstract Structural, dielectric and magnetic properties of nano-size polycrystalline, La2CuMnO6 (LCM) samples were studied in the temperature range 80 K to 300 K. Orthorhombic single phase with space group 'Pnma' was confirmed by Rietveld refinement of XRD peaks. The small-polaron driven dielectric dispersion showed relaxation peaks in the vicinity of low-temperatures. The X-ray absorption spectroscopy (XAS) confirmed the charge states of Cu (2+) and Mn (4+) ions. DC-resistivity analysis supported the thermally activated conduction for high temperature and the variable range hoping (VRH) mechanism of conduction at low-temperature. The deviation of super-exchange angles between B-site cations from an ideal 180º value produced non-collinearity in the antiferromagnetic response of this ceramic and was confirmed canted antiferromagnetic behaviour. Positive Curie temperature along with finite coercivity indicated that the super-exchange interaction between Cu2+ and Mn4+ ions influenced the magnetic behaviour of this ceramics and showed a heterogenous magnetic response.

scholarly journals Al-driven peculiarities of local coordination and magnetic properties in single-phase Alx-CrFeCoNi high-entropy alloys

Nano Research ◽  
2021 ◽  
Author(s):  
Alevtina Smekhova ◽  
Alexei Kuzmin ◽  
Konrad Siemensmeyer ◽  
Chen Luo ◽  
Kai Chen ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Magnetic Circular Dichroism ◽  
Surface Region ◽  
Face Centered Cubic ◽  
X Rays ◽  
X Ray ◽  
High Entropy ◽  
X Ray Absorption ◽  
Absorption Edges

AbstractModern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic properties. Herein, peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic (fcc)- and body-centered cubic (bcc)-structured high-entropy Alx-CrFeCoNi alloys (x = 0.3 and 3, respectively) are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy ranges. Simulations based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high precision. The revealed unimodal and bimodal distributions of all five elements are in agreement with structure-dependent magnetic properties of studied alloys probed by magnetometry. A degree of surface atoms oxidation uncovered by soft X-rays suggests different kinetics of oxide formation for each type of constituents and has to be taken into account. X-ray magnetic circular dichroism technique employed at L2.3 absorption edges of transition metals demonstrates reduced magnetic moments of 3d metal constituents in the sub-surface region of in situ cleaned fcc-structured Al0.3-CrFeCoNi compared to their bulk values. Extended to nanostructured versions of multicomponent alloys, such studies would bring new insights related to effects of high entropy mixing on low dimensions.

scholarly journals The Study of Magnetic Properties for Non-Magnetic Ions Doped BiFeO3

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4061
Author(s):  
Yongtao Li ◽  
Liqing Liu ◽  
Dehao Wang ◽  
Hongguang Zhang ◽  
Xuemin He ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Local Structure ◽  
Metal Ion ◽  
Single Phase ◽  
Sol Gel ◽  
X Ray ◽  
Co Doping ◽  
Magnetic Ions ◽  
X Ray Absorption ◽  
Fe Ions

BiFeO3 is considered as a single phase multiferroic. However, its magnetism is very weak. We study the magnetic properties of BiFeO3 by Cu and (Cu, Zn). Polycrystalline samples Bi(Fe0.95Cu0.05)O3 and BiFe0.95(Zn0.025Cu0.025)O3 are prepared by the sol-gel method. The magnetic properties of BiFe0.95(Zn0.025Cu0.025)O3 are greater than that of BiFeO3 and Bi(Fe0.95Cu0.05)O3. The analyses of X-ray absorption fine structure data show that the doped Cu atoms well occupy the sites of the Fe atoms. X-ray absorption near edge spectra data confirm that the valence state of Fe ions does not change. Cu and Zn metal ion co-doping has no impact on the local structure of the Fe and Bi atoms. The modification of magnetism by doping Zn can be understood by the view of the occupation site of non-magnetically active Zn2+.

Effects of Lattice Defects on Cathode Properties of LiMn2O4 Synthesized at Low Temperatures for Lithium Ion Secondary Battery

2008 ◽  
Vol 388 ◽  
pp. 41-44 ◽  
Author(s):  
Hiroyuki Kaiya ◽  
Shinya Suzuki ◽  
Masaru Miyayama
Keyword(s):  
Absorption Spectroscopy ◽  
Low Temperatures ◽  
Heating Temperature ◽  
Sol Gel ◽  
Lithium Ion ◽  
Lattice Defects ◽  
X Ray ◽  
Secondary Battery ◽  
Cation Mixing ◽  
X Ray Absorption

Effects of lattice defects on cathode properties of LiMn2O4 synthesized at low temperatures were investigated. LiMn2O4 powders were synthesized by a sol-gel method. The specific capacities of LiMn2O4 decreased from 134 to 81 mAh g-1 with decreasing heating temperature from 750 to 200°C. X-ray absorption spectroscopy showed that a large amount of lattice defects such as cation vacancies existed and cation mixing occurred in LiMn2O4 calcined at low temperatures. It was found that the low specific capacities of LiMn2O4 calcined at low temperatures were attributed to these lattice defects.

Evolution of Ce-Valence in Ce-Rh-Si Compounds: Intermediate Valence in CeRh6Si4

2016 ◽  
Vol 257 ◽  
pp. 199-202
Author(s):  
Thomas Gruner ◽  
Christoph Geibel
Keyword(s):  
Ground State ◽  
Low Temperatures ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Intermediate Valence ◽  
Characteristic Energy ◽  
X Ray ◽  
Resistivity Measurements ◽  
Intermediate Valent ◽  
X Ray Absorption

We synthesized polycrystalline samples of CeRh6Si4 and investigated its physical properties by means of magnetic susceptibility, specific heat and electrical resistivity measurements as well as LIII X-ray absorption spectroscopy. All results evidence an intermediate-valent (IV) Ce state with a valence close to 3.2 and a characteristic energy of about 300 K. Accordingly, we observe a Fermi liquid ground state at low temperatures with a slightly enhanced Sommerfeld coefficient γ = 28 mJ/molK2. Using presently available data on different compounds, we analyze the evolution of the Ce valence in the Ce-Rh-Si ternary phase diagram. The expected correlation with the distance to nearest Ce-ligands can be discerned. Thus, the evolution from a trivalent Ce3+ state in CeRh3Si2 to an IV state in CeRh6Si4 is related to a shortening of both the Ce-Rh and Ce-Si bonds in the first coordination sphere of Ce.

Silicide Formation in High-Dose Fe-Implanted Silicon

1991 ◽  
Vol 235 ◽  
Author(s):  
Z. Tan ◽  
F. Namavar ◽  
S. M. Heald ◽  
J. I. Budnick ◽  
F. H. Sanchez
Keyword(s):  
Fine Structure ◽  
Single Phase ◽  
Rutherford Backscattering Spectrometry ◽  
High Dose ◽  
Silicide Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Implantation Damage ◽  
X Ray Absorption ◽  
Post Implantation

ABSTRACTWe have studied the silicide formation in Fe-implanted Si(100), with 1×1017-1×1018 Fe/cm2, using extended x-ray-absorption fine structure (EXAFS), x-ray diffraction and Rutherford backscattering spectrometry (RBS) methods. In the samples as-implanted at 350 °C, no silicide was observed at doses below 3×1017 Fe/cm2. At 5×1017 Fe/cm2, both α-FeSi2 and (β-FeSi2 form but α-FeSi2 appears to be the majority phase. As the dose increases to 7×1017 and above, ordered FeSi forms, but implantation damage is severe and a large number of Fe atoms are in very disordered environments. In addition to FeSi, Fe5Si3 was also observed in the 1×1018 Fe/cm2 sample. Upon post-implantation annealing at 700 °C or 900 °C, single phase P-FeSi2 was obtained independent of the dosage.

Experimental verification of the need for either jj or intermediate coupling in the 5f states of plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
K. T. Moore ◽  
M. A. Wall ◽  
A. J. Schwartz ◽  
B. W. Chung ◽  
J. G. Tobin ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Electron Microscope ◽  
Synchrotron Radiation ◽  
Single Phase ◽  
High Spatial Resolution ◽  
Intermediate Coupling ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Energy Loss ◽  
X Ray Absorption

ABSTRACTHere, we demonstrate the power of electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) to investigate the electronic structure plutonium. Using EELS, TEM, and synchrotron-radiation-based X-ray absorption spectroscopy (XAS), we provide the first experimental evidence that Russell-Saunders (LS) coupling fails for the 5f states of Pu. These results support the assumption that only the use of jj or intermediate coupling is appropriate for the 5f states of Pu. EELS experiments were performed in a TEM and are coupled with image and diffraction data, therefore, the measurements are completely phase specific. It is shown that EELS in a TEM may be used to circumvent the difficulty of producing single-phase or single-crystal samples due to its high spatial resolution.

The Structure and Ferromagnetic Properties of the Single Phase Bi0.95Eu0.05Fe0.95Co0.05O3 Nanoparticles Prepared by Sol-Gel

2012 ◽  
Vol 512-515 ◽  
pp. 1434-1437
Author(s):  
Xing Ao Li ◽  
Peng Li ◽  
Yong Tao Li ◽  
Jian Ping Yang ◽  
Qiu Fei Bai ◽  
...  
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Mixed Valence ◽  
Magnetic Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Valence States ◽  
Sol Gel Process ◽  
X Ray Absorption ◽  
Fe Ions

Bi0.95Eu0.05Fe0.95Co0.05O3 Nanoparticles sample was prepared by sol-gel process. The microstructure of samples was analysised by X-ray diffraction(XRD), the result indicated that it was the single phase rhombohedral perovskite structure. The morphology of samples was measured by scanning electron microsopy(SEM), the SEM photograph of samples indicated that the nanoparticles of Bi0.95Eu0.05Fe0.95Co0.05O3 sample were small than that of BiFeO3. The valence states of Fe ions in the samples was analysised by the X-ray absorption spectroscopy（XAS）. The XAS of Fe2p showed that it was the mixed valence states (Fe2+ and Fe3+) of Fe ions in samples, and the binding energy of Bi0.95Eu0.05Fe0.95Co0.05O3 was bigger than that of BiFeO3.The magnetic characteristics of the samples were measured by vibrating sample magnetometer (VSM)，the results showed that the weak metamagnetism were obtained from clear hysteresis loop and the magnetic saturation reached 0.408emu/g，compared with BiFeO3 sample, the magnetic properties were significantly enhanced.

Local structure anomalies of the BaBi(Pb)O3 system at low temperatures: an X-ray absorption study

1997 ◽  
Vol 277 (3-4) ◽  
pp. 257-264 ◽  
Author(s):  
A.P. Menushenkov ◽  
S. Benazeth ◽  
J. Purans ◽  
A.Yu. Ignatov ◽  
K.V. Klementev
Keyword(s):  
Local Structure ◽  
Low Temperatures ◽  
Absorption Study ◽  
X Ray ◽  
X Ray Absorption

Magnetic behaviour of trioctahedral mica-2M1 occurring in a magnetic anomaly zone

2008 ◽  
Vol 72 (5) ◽  
pp. 1035-1042 ◽  
Author(s):  
S. Pini ◽  
M. Affronte ◽  
M. F. Brigatti
Keyword(s):  
Magnetic Susceptibility ◽  
Peak Position ◽  
Magnetic Behaviour ◽  
Ac Magnetic Susceptibility ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Trioctahedral Mica ◽  
Two Peaks ◽  
X Ray Absorption

AbstractThis work relates the crystal chemistry and the magnetic behaviour of a trioctahedral mica (chemical formula: (K0.90Na0.01Ca0.01Ba0.01 ☐0.07)(Al0.05Fe2+1.10Mg1.38Ti0.32Mn0.01☐0.04)(Al1.12Si2.88)O10 (F0.27OH1.27O0.46); unit cell parameters: a = 5.345(2) Å, b = 9.261(4) Å, c = 20.189(8) Å; β = 95.075(8)°) from Minto Block (Ungava peninsula, northern Quebec, Canada), a region characterized by high magnetic anomalies. Crystallographic and X-ray absorption spectroscopy data suggest a prevalent divalent oxidation state for Fe and a disordered Fe 2+ distribution in the two octahedral sites Ml and M2. The real part of magnetic susceptibility shows two peaks at ∼5.2 K and 120 K. However, as demonstrated by AC magnetic susceptibility measurements, the origin of the two effects is different: the peak position of the first one (i.e. the effect revealed at 5.2 K) is frequency-dependent, thus suggesting a spin-glass like behaviour. The effect at 120 K can instead be attributed to the occurrence of diluted phases in mica matrix, such as Fe oxides.

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