scholarly journals Structural, magnetic and electrical properties of a new double-perovskite LaNaMnMoO 6 material

2017 ◽  
Vol 4 (11) ◽  
pp. 170920 ◽  
Author(s):  
Sameh Megdiche Borchani ◽  
Wissem Cheikh-Rouhou Koubaa ◽  
Makrem Megdiche
Keyword(s):  
Applied Field ◽  
Room Temperature ◽  
Double Perovskite ◽  
Entropy Change ◽  
Cooling Power ◽  
Room Temperature Resistivity ◽  
Ferromagnetic Transition ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Xrd Patterns

Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO 6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature T C is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO 6 sample as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of T C , |−ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg −1  K −1 . Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A 2 FeMoO 6 (A = Sr, Ba) double-perovskite system.

scholarly journals Structural, Magnetic, and Magnetocaloric Properties of R2NiMnO6 (R = Eu, Gd, Tb)

2021 ◽  
Author(s):  
K.P. Shinde ◽  
E.J. Lee ◽  
Maykel Manawan ◽  
A. Lee ◽  
S.Y. Park ◽  
...  
Keyword(s):  
Magnetic Entropy Change ◽  
Ceramic Powder ◽  
Double Perovskite ◽  
Entropy Change ◽  
Cooling Power ◽  
X Ray Diffraction ◽  
Atomic Size ◽  
X Ray ◽  
Magnetocaloric Properties ◽  
Group A

Abstract Double perovskite Eu2NiMnO6 (ENMO) Gd2NiMnO6 (GNMO) and Tb2NiMnO6 (TNMO) ceramic powder have been synthesized by solid-state reaction and their crystal structure, microstructure, cryogenic magnetic properties, and magnetocaloric performance have been investigated. Structural studies by using X-ray diffraction shows that all compounds crystallize in the monoclinic structure with a P21/n space group. A ferromagnetic to paramagnetic (FM-PM) second-order phase transition occurred in ENMO, GNMO, and TNMO around 143, 130, and 112 K, respectively. The values of maximum magnetic entropy change and relative cooling power at an applied field of 5 T are found to be 3.2, 3.8, 3.5 J/kgK and 150, 182, 176 J/kg respectively, for the studied sample. The change in structural, magnetic, and magnetocaloric effect ascribed to the superexchange mechanism of Ni2+ – O – Mn3+ and Ni2+ – O – Mn4+. Due to different atomic size of Eu, Gd, Tb changes the ratio of Mn4+/Mn3+ which is responsible for the variation of properties significantly in double perovskite.

Tailoring the Magnetic Properties and Magnetocaloric Effect in Double Perovskites Sr2FeMo1–xNbxO6

2020 ◽  
Vol 12 (3) ◽  
pp. 391-397 ◽  
Author(s):  
Imad Hussain ◽  
S. N. Khan ◽  
Tentu Nageswara Rao ◽  
Riyaz Uddin ◽  
Jong Woo Kim ◽  
...  
Keyword(s):  
Magnetic Measurements ◽  
Spontaneous Magnetization ◽  
Double Perovskite ◽  
Entropy Change ◽  
Solid State Reaction Method ◽  
Cooling Power ◽  
X Ray Diffraction ◽  
Site Disorder ◽  
Magnetocaloric Properties ◽  
Arrott Plots

The crystal structure, magnetic and magnetocaloric properties of the Sr2FeMo1–xNbxO6 (0 ≤ x ≤ 0.3) samples prepared by solid state reaction method were investigated using X-ray diffraction (XRD) and magnetic measurements. The room temperature XRD profiles obtained for all the samples revealed the formation of the double perovskite tetragonal structure with I4/mmm symmetry. Maximum values of spontaneous magnetization (17.6 emu/g at 150 K) and Curie temperature, TC (380 K) were observed in the Sr2FeMo0.9Nb0.1O6 sample indicating that low Niobium (Nb) substitution (x = 0.1) at the Mo site in the host material resulted in higher magnetization and TC. Lower values of magnetization and TC were recorded in the samples with higher Nb concentration (x = 0.2, 0.3) that was attributed to the decrease in orbital hybridization and increase in anti-site disorder resulting from heavy doping. A second order of the magnetic phase transition in each sample was confirmed by the magnetization measurements and Arrott plots. The maximum magnetic entropy change and relative cooling power (RCP) were enhanced in lowest Nb doped sample (x = 0.1) suggesting that this compound can be used in magnetic refrigeration technology.

STRUCTURE AND MAGNETIC PROPERTIES OF MECHANICAL ALLOYED Mn-15at.%Al

2013 ◽  
Vol 12 (01) ◽  
pp. 1350006
Author(s):  
AHMED E. HANNORA ◽  
FARIED F. HANNA ◽  
LOTFY K. MAREI
Keyword(s):  
Thermal Analysis ◽  
Room Temperature ◽  
Average Crystallite Size ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Milled Sample ◽  
Powder Samples ◽  
Xrd Patterns ◽  
Method Analysis

Mechanical alloying (MA) method has been used to produce nanocrystallite Mn -15at.% Al alloy. X-ray diffraction (XRD) patterns for the as-milled elemental α- Mn and aluminum powder samples show a mixture of α + β- MnAl phases after 20 h of milling and changes to a dominant β- MnAl phase structure after 50 h. An average crystallite size of 40 nm was determined from Hall–Williamson method analysis after 5 h of milling. Moreover, the thermal analysis results using differential thermal analysis (DTA), suggested a possible phase transformation after 20 h of milling. Isothermal treatments are carried in the temperature range of 450°C to 1000°C. Room-temperature vibrating sample magnetometer (VSM) measurements of the hysteretic response revealed that the saturation magnetization Bs and coercivity Hc for 10 h ball milled sample are ~ 2.1 emu/g and ~ 92 Oe, respectively.

INFLUENCE OF GRAIN SIZE ON MAGNETOCALORIC EFFECT IN THE NANOCRYSTALLINELa0.8Te0.2MnO3

2011 ◽  
Vol 10 (04n05) ◽  
pp. 597-600
Author(s):  
RABINDRA NATH MAHATO ◽  
K. SETHUPATHI ◽  
V. SANKARANARAYANAN
Keyword(s):  
Grain Size ◽  
Landau Theory ◽  
Sol Gel ◽  
Entropy Change ◽  
Ferromagnetic Transition ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Paramagnetic Region ◽  
Rhombohedral Crystal Structure ◽  
Crystallite Sizes

The nanocrystalline La0.8Te0.2MnO3samples are prepared by sol-gel method and show rhombohedral crystal structure with R3c space group at room temperature. The calculated crystallite sizes are ~55 nm, 40 nm and 25 nm for calcined at 700°C, 800°C and 900°C temperatures. The SEM images show the grain size increases as the calcination temperature increases and the values are in good agreement with that obtained from X-ray diffraction analysis. The samples undergo paramagnetic to ferromagnetic transition and follow Curie–Weiss law in the paramagnetic region. The maximum entropy change are ~3.2 J kg-1K-1, 3 J kg-1K-1and 2 J kg-1K-1for a field change of 20 kOe for 55 nm, 40 nm and 25 nm samples respectively. In the framework of Landau theory of phase transition, the experimentally observed magnetic entropy change and theoretical predicted model fits well for all the nanoparticles.

scholarly journals Formation of Metastable Disordered Ni3Al by Pulsed Laser Induced Rapid Solidification

1990 ◽  
Vol 213 ◽  
Author(s):  
Jeffrey A. West ◽  
James T. Manos ◽  
Michael J. Aziz
Keyword(s):  
Rapid Solidification ◽  
Room Temperature ◽  
Interface Velocity ◽  
Phase Changes ◽  
Fast Time ◽  
Room Temperature Resistivity ◽  
X Ray Diffraction ◽  
Resistivity Measurements ◽  
Disordered Lattice ◽  
Transmission Electron

ABSTRACTThin films of Ni3Al formed by co-evaporation onto insulating substrates form a single phase fcc disordered lattice upon rapid solidification following excimer laserinduced melting with an interface velocity of ~4 m/s. Transmission Electron Microscopy (TEM) and x-ray diffraction (XRD) analyses exhibit no superlattice diffraction at room temperature. Resistivity measurements, indicating that the disordered phase has a higher resistivity and much smaller temperature coefficient at room temperature than the stable ordered (L12) phase, permit us to monitor phase changes and ordering on a fast time-scale. Subsequent annealing recovers long-range order, with resistivity measurements indicating that reordering begins just below 300°C.

Solid Solutions Study of BaTiO3 Doped on B Site by Electronic Compensation

2014 ◽  
Vol 976 ◽  
pp. 30-35
Author(s):  
Francisco Raúl Barrientos-Hernández ◽  
Alberto Arenas-Flores ◽  
Iván Alonso Lira Hernández ◽  
Carlos Gómez-Yáñez ◽  
Miguel Pérez Labra
Keyword(s):  
Room Temperature ◽  
Hexagonal Phase ◽  
Ferroelectric Properties ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Solid State Method ◽  
X Ray ◽  
Air Atmosphere ◽  
Conventional Solid State Method ◽  
Electronic Compensation

Several compositions of BaTiO:Nb5+ were made by conventional solid-state method in air atmosphere, according to the general formula BaTi1-xNbxO3; (x= 0.005, 0.04, 0.08, 0.20, and 0.25). The crystal structure, microstructure, dielectric and ferroelectric properties of samples were investigated by XRD, Raman Spectroscopy, Electrical Measurements and SEM. X-ray diffraction results clearly indicated that when x ≥ 0.25 was prepared; the hexagonal phase Ba8Ti3Nb4O24 appeared. Electrical measurements at 1 kHz were carried out and several pellets were made, the relative permittivity was calculated. The dielectric constant of the pristine BaTiO3 is about 7000, and the Curie temperature is ≈120°C at room temperature, decreasing to 90°C with Nb5+ addition (x = 0.005).

An X-ray diffraction system with controlled relative humidity and temperature

1996 ◽  
Vol 11 (4) ◽  
pp. 288-289 ◽  
Author(s):  
H. Hashizume ◽  
S. Shimomura ◽  
H. Yamada ◽  
T. Fujita ◽  
H. Nakazawa ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Control Unit ◽  
Saturated Water Vapor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Saturated Water ◽  
Sample Chamber ◽  
Diffraction Patterns ◽  
Xrd Patterns

A system enabling X-ray diffraction patterns under controlled conditions of relative humidity and temperature has been devised and combined with an X-ray powder diffractometer. Relative humidity in the sample space is controlled by mixing dry N2 gas with saturated water vapor. Temperatures of the sample and inner wall of the sample chamber are monitored by two attached thermocouples and the information was fed back to the control unit. Relative humidity between 0% and the 95%, and temperature between room temperature and 60 °C can be controlled. All parameters including those for XRD are programmable and the system runs automatically. The function of the system was checked by recording the XRD patterns of montmorillonite (a clay mineral) and NaCl under increasing and decreasing relative humidity.

Magnetic Properties and Magnetocaloric Effect of Nd0.7Gd0.3Mn2Si2 Alloy

2017 ◽  
Vol 1142 ◽  
pp. 47-52 ◽  
Author(s):  
Shi Dong Lin ◽  
Xiao Long Chen ◽  
Jiang Wang ◽  
Chao Fan Zhu ◽  
Mao Hua Rong ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetocaloric Effect ◽  
Physical Property Measurement System ◽  
Physical Property ◽  
Entropy Change ◽  
Spin Reorientation ◽  
Cooling Power ◽  
Field Change ◽  
X Ray Diffraction ◽  
Scanning Calorimetry

In this work, crystal structure, magnetic properties and magnetocaloric effect of Nd0.7Gd0.3Mn2Si2 alloy were studied by X-ray diffraction (XRD), Physical Property Measurement System (PPMS) and Differential Scanning Calorimetry (DSC). Nd0.7Gd0.3Mn2Si2 crystallizes in ThCr2Si2-typed structure with space group I4/mmm, in which the Nd, Gd, Mn and Si atoms occupy 2a (0, 0, 0), 2a (0, 0, 0), 4d (0, 1/2, 1/4) and 4e (0, 0, 0.38261) position, respectively. The Curie temperature (Tc) of Nd0.7Gd0.3Mn2Si2 alloy is 42 K, while the spin reorientation temperature (TSR) is 26 K and the Nel temperature (TN) is 410 K. The Tc and TN were determined using PPMS and DSC, respectively. The maximum value of the magnetic entropy change (-Smax) in the field change of 0-5 T is 11.862 J/kg K, while the value of relative cooling power (RCP) in Nd0.7Gd0.3Mn2Si2 alloy is 69.666 J/kg under the field change of 5 T.

scholarly journals The Effect of Fe Doping on the Magnetic and Magnetocaloric Properties of Mn5−xFexGe3

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Jeffrey Brock ◽  
Nathanael Bell-Pactat ◽  
Hong Cai ◽  
Timothy Dennison ◽  
Tucker Fox ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
Entropy Change ◽  
Second Order ◽  
Ferromagnetic Transition ◽  
Fe Doping ◽  
First Order Phase Transition ◽  
Magnetocaloric Properties ◽  
First Order Phase

The magnetic and magnetocaloric properties of a series of minutely doped Mn5-xFexGe3 compounds that exhibit the D88-type hexagonal crystal structure at room temperature have been investigated. For all Fe concentrations, the alloys are ferromagnetic and undergo a second-order ferromagnetic-to-paramagnetic transition near room temperature. Although the small Fe doping had little effect on the ferromagnetic transition temperatures of the system, changes in the saturation magnetization and magnetic anisotropy were observed. For x≤0.15, all compounds exhibit nearly the same magnetic entropy change of ~7 J/kg K, for a field change of 50 kOe. However, the magnitude of the refrigerant capacities increased with Fe doping, with values up to 108.5 J/kg and 312 J/kg being observed for field changes of 20 kOe and 50 kOe, respectively. As second-order phase transition materials, the Mn5-xFexGe3 compounds are not subject to the various drawbacks associated with first-order phase transition materials yet exhibit favorable magnetocaloric effects.

scholarly journals XRD and TG-DTA Study of New Phosphate-Based Geopolymers with Coal Ash or Metakaolin as Aluminosilicate Source and Mine Tailings Addition

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 202
Author(s):  
Dumitru Doru Burduhos Nergis ◽  
Petrica Vizureanu ◽  
Andrei Victor Sandu ◽  
Diana Petronela Burduhos Nergis ◽  
Costica Bejinariu
Keyword(s):  
Mine Tailings ◽  
Room Temperature ◽  
Raw Materials ◽  
Coal Ash ◽  
Water Evaporation ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
Xrd Patterns ◽  
First Time ◽  
Alkali Activated

Coal ash-based geopolymers with mine tailings addition activated with phosphate acid were synthesized for the first time at room temperature. In addition, three types of aluminosilicate sources were used as single raw materials or in a 1/1 wt. ratio to obtain five types of geopolymers activated with H3PO4. The thermal behaviour of the obtained geopolymers was studied between room temperature and 600 °C by Thermogravimetry-Differential Thermal Analysis (TG-DTA) and the phase composition after 28 days of curing at room temperature was analysed by X-ray diffraction (XRD). During heating, the acid-activated geopolymers exhibited similar behaviour to alkali-activated geopolymers. All of the samples showed endothermic peaks up to 300 °C due to water evaporation, while the samples with mine tailings showed two significant exothermic peaks above 400 °C due to oxidation reactions. The phase analysis confirmed the dissolution of the aluminosilicate sources in the presence of H3PO4 by significant changes in the XRD patterns of the raw materials and by the broadening of the peaks because of typically amorphous silicophosphate (Si–P), aluminophosphate (Al–P) or silico-alumino-phosphate (Si–Al–P) formation. The phases resulted from geopolymerisation are berlinite (AlPO4), brushite (CaHPO4∙2H2O), anhydrite (CaSO4) or ettringite as AFt and AFm phases.

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