References of "Sougrati, Moulay Tahar"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailA study of the high temperature spin reorientation in YCoFe/sub 3/B
Grandjean, Fernande ULg; Sougrati, Moulay Tahar ULg; Mayot, H. et al

in Journal of Physics : Condensed Matter (2009), 21(18), 1860017-1860017

The iron-57 Mossbauer spectra of YCoFe /sub 3/ B have been measured between 4.2 and 480 K and reveal that YCoFe /sub 3/ B exhibits an axial orientation of the iron magnetic moments below 450 K and a basal ... [more ▼]

The iron-57 Mossbauer spectra of YCoFe /sub 3/ B have been measured between 4.2 and 480 K and reveal that YCoFe /sub 3/ B exhibits an axial orientation of the iron magnetic moments below 450 K and a basal orientation above 450 K. This spin reorientation, also observed in the thermomagnetic curves, results from the different signs of the contributions to the magnetic anisotropy of the 2c and 6i sites that are occupied by iron. The neutron diffraction patterns of YCoFe /sub 3/ B have been measured at 2 K and between 290 and 770 K and have been successfully analyzed with a model compatible with the magnetic orientation obtained from the Mossbauer spectra. The hybridization between the cobalt or iron 3d orbitals and the boron 2p orbitals leads to a larger magnetic moment and hyperfine field on the 2c site as compared to the 6i site. [less ▲]

Detailed reference viewed: 23 (5 ULg)
Full Text
Peer Reviewed
See detailStructural and magnetic properties of Pr18Li8Fe5-xMxO39 (M = Ru, Mn, Co)
Dutton, Sian E; Battle, Peter D; Grandjean, Fernande ULg et al

in Journal of Solid State Chemistry (2009), 182(7), 1638-1648

A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mossbauer spectroscopy; samples of Pr18Li8Fe5 ... [more ▼]

A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mossbauer spectroscopy; samples of Pr18Li8Fe5-xMxO39 and Pr18Li8Fe5-xCoxO39 (x = 1, 2) have been studied by magnetometry. All these Compounds adopt a cubic structure (space group Pm (3) over barn, a(o)similar to 11.97 angstrom) based on intersecting < 111 > chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr-O framework. The trigonal-prismatic site in Pr18Li8Fe4RuO39 is occupied by Li+ and high-spin Fe3+. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr18Li8Fe4RuO39) or below. (C) 2009 Elsevier Inc. All rights reserved. [less ▲]

Detailed reference viewed: 32 (0 ULg)
Full Text
Peer Reviewed
See detailA structural, magnetic and Mössbauer spectral study of the magnetocaloric Mn1.1Fe0.9P1-xGex compounds
Sougrati, Moulay Tahar ULg; Hermann, Raphaël ULg; Grandjean, Fernande ULg et al

in Journal of Physics : Condensed Matter (2008), 20

The structural, magnetic and Mössbauer spectral properties of the magnetocaloric Mn1.1Fe0.9P1−xGex compounds, with 0.19 < x < 0.26, have been measured between 4.2 and 295 K. The 295 K unit-cell volume ... [more ▼]

The structural, magnetic and Mössbauer spectral properties of the magnetocaloric Mn1.1Fe0.9P1−xGex compounds, with 0.19 < x < 0.26, have been measured between 4.2 and 295 K. The 295 K unit-cell volume increases from x = 0.19 to 0.22 and is substantially smaller in the ferromagnetic Mn1.1Fe0.9P0.74Ge0.26. The temperature dependence of the magnetization reveals a ferromagnetic to paramagnetic transition with a Curie temperature between approximately 250 and 330 K and hysteresis width of 10 to 4 K, for 0.19 < x < 0.25. The composition Mn1.1Fe0.9P0.78Ge0.22 shows the largest isothermal entropy change of approximately 10 J/(kgKT) at 290 K. The M¨ossbauer spectra have been analysed with a binomial distribution of hyperfine fields correlated with a change in isomer shift and quadrupole shift, a distribution that results from the distribution of phosphorus and germanium among the near neighbours of the iron. The coexistence of paramagnetic and magnetically ordered phases in ranges of temperature of up to 50 K around the Curie temperature is observed in the Mössbauer spectra and is associated with the first-order character of the ferromagnetic to paramagnetic transition. The temperature dependence of the weighted average hyperfine field is well fitted within the magnetostrictive model of Bean and Rodbell. Good fits of the Mössbauer spectra could only be achieved by introducing a difference between the isomer shifts in the paramagnetic and ferromagnetic phases, a difference that is related to the magnetostriction and electronic structure change. [less ▲]

Detailed reference viewed: 54 (15 ULg)
Full Text
See detailCorrosion atmosphérique des bronzes et Spectroscopie Mössbauer.
Sougrati, Moulay Tahar ULg

Doctoral thesis (2008)

The aim of this work is to improve our understanding of the atmospheric corrosion of bronzes. This work focuses on three axes: - The characterization of tin compounds expected in atmospheric corrosion ... [more ▼]

The aim of this work is to improve our understanding of the atmospheric corrosion of bronzes. This work focuses on three axes: - The characterization of tin compounds expected in atmospheric corrosion. The Mössbauer spectroscopy which has been the main tool in our multianalytical approach, allows selective and quantitative analysis. The Mössbauer parameters and f-factors have been determined for many tin oxides, chlorides and sulfates. The f-factors are different from a compound to another and highly T-dependent which justify low temperature Mössbauer measurements. - The development of a low temperature CEMS detector to permit low temperature and non-destructive surface analysis. The detector operation has been optimized for various gases between 41 and 300 K. - The 2-years outdoor exposure in an urban site including CuSn9, CuSn3Zn9 bronzes, CuZn33 brass and pure metals. The corrosion and runoff rates have been investigated as well as the role of alloying elements in corrosion process. [less ▲]

Detailed reference viewed: 621 (34 ULg)
Full Text
Peer Reviewed
See detailPhase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra
McGuire, Michael A; Christianson, Andrew D; Sefat, Athena S et al

in Physical Review. B (2008), 78(9),

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal ... [more ▼]

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal-orthorhombic crystallographic phase transition at similar to 160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder x-ray and neutron-diffraction measurements is presented. A magnetic moment of similar to 0.35 mu(B) per iron is derived from Mossbauer spectra in the low-temperature phase. Evidence of the structural transition is observed at temperatures well above the transition temperature (up to near 200 K) in the diffraction data as well as the polycrystalline elastic moduli probed by resonant ultrasound spectroscopy measurements. The effects of the two phase transitions on the transport properties (resistivity, thermal conductivity, Seebeck coefficient, and Hall coefficient), heat capacity, and magnetization of LaFeAsO are also reported, including a dramatic increase in the magnitude of the Hall coefficient below 160 K. The results suggest that the structural distortion leads to a localization of carriers on Fe, producing small local magnetic moments which subsequently order antiferromagnetically upon further cooling. Evidence of strong electron-phonon interactions in the high-temperature tetragonal phase is also observed. [less ▲]

Detailed reference viewed: 120 (37 ULg)
Full Text
Peer Reviewed
See detailHyperfine interactions and lattice dynamics of Sn21O6Cl16(OH)(14)
Sougrati, Moulay Tahar ULg; Jouen, S.; Hannoyer, Béatrice et al

in Journal of Solid State Chemistry (2008), 181(9), 2473-2479

In this study, the tin(II) oxy-hydroxychloride Sn21O6Cl16(OH)(14) has been synthesised and investigated, This compound is the synthetic equivalent of mineral abhurite, which was discovered in 1985 as a ... [more ▼]

In this study, the tin(II) oxy-hydroxychloride Sn21O6Cl16(OH)(14) has been synthesised and investigated, This compound is the synthetic equivalent of mineral abhurite, which was discovered in 1985 as a tin corrosion product formed on the surface of tin ingots after long immersion in seawater. The Mossbauer parameters of Sn(21)O6Cl(16)(OH)(14) determined at various temperatures are reported and discussed for the first time. At room temperature, the isomer shift and the quadrupole splitting are, respectively, delta = 3.22 mm s(-1) and Delta = 1.71 mm s(-1) relative to the centroid of the spectrum of BaSnO3. ne Mossbauer recoil-free fraction has been also evaluated over a wide range of temperature. At 300 K, the recoil-free fraction of Sn21O6Cl16(OH)(14) is f(300) = 0.09 +/- 0.02. (C) 2008 Elsevier Inc. All rights reserved. [less ▲]

Detailed reference viewed: 44 (8 ULg)
Full Text
Peer Reviewed
See detailFourier transform infrared spectroscopic study of abhurite Sn21O6Cl16(OH)(14)
Jouen, Samuel; Lefez, Benoit; Sougrati, Moulay Tahar ULg et al

in Materials Chemistry & Physics (2007), 105(2-3), 189-193

Abhurite Sn21O6Cl16(OH)(14) is a tin oxy-hydroxychloride discovered in 1985 as a tin corrosion product formed after long immersion in seawater, has been synthesised and studied using FTIRAS analysis. The ... [more ▼]

Abhurite Sn21O6Cl16(OH)(14) is a tin oxy-hydroxychloride discovered in 1985 as a tin corrosion product formed after long immersion in seawater, has been synthesised and studied using FTIRAS analysis. The vibrational spectra obtained in transmission and reflectance modes of analysis are presented and compared to the vibrational spectra determined by Kramers-Kronig analysis. Transversal and longitudinal (TO and LO) optical modes have been identified. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 42 (10 ULg)
Full Text
Peer Reviewed
See detailRelative Lamb-Mossbauer factors of tin corrosion products
Sougrati, Moulay Tahar ULg; Jouen, S.; Hannoyer, Béatrice

in Hyperfine Interactions (2006), 167(1-3), 815-818

Variable temperature Sn-119 Mossbauer spectroscopy was used to obtain relative Lamb-Mossbauer factors for three tin corrosion products: hydrated stannic oxide SnO2 center dot xH(2)O, abhurite Sn21O6Cl16 ... [more ▼]

Variable temperature Sn-119 Mossbauer spectroscopy was used to obtain relative Lamb-Mossbauer factors for three tin corrosion products: hydrated stannic oxide SnO2 center dot xH(2)O, abhurite Sn21O6Cl16(OH)(14), and tin hydroxysulfate Sn3OSO4(OH)(2). Their hyperfine parameters have also been investigated. [less ▲]

Detailed reference viewed: 59 (9 ULg)
Peer Reviewed
See detailA Study of Copper and Copper Alloys Runoff in Urban Atmosphere
Sougrati, Moulay Tahar ULg; Jouen, Samuel; Hannoyer, Béatrice

in Welter, Jean-Marie (Ed.) Copper (2006)

The runoff rates of copper and copper alloys CuSn9 and CuSn3Zn9 have been studied along a field exposure of one year in an urban area located in upper Normandy region in northern France. Mass measurements ... [more ▼]

The runoff rates of copper and copper alloys CuSn9 and CuSn3Zn9 have been studied along a field exposure of one year in an urban area located in upper Normandy region in northern France. Mass measurements of samples, analysis of the adherent corrosion layers and runoff rates of metals were carried out throughout the exposure time. Runoff rates turn to be relatively stable during the exposure time. The influence of alloying elements on the copper runoff rate has been studied and it was demonstrated that addition of zinc permit to decrease the amount of copper that releases from the corroded surface by rainfall. Concerning the tin content, no significant influence has been observed on the copper runoff [less ▲]

Detailed reference viewed: 44 (7 ULg)