M. Guillot

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (204)394.17 Total impact

  • V. Paul-Boncour · M. Guillot · T. Mazet
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    ABSTRACT: In this work are presented results on the structural, magnetic, and magnetocaloric properties of the Y0.9Gd0.1Fe2D4.2 compound in which TM0 is shifted from 84 K to 110 K because of Gd influence. Magnetization measurements have been performed with a magnetic field up to 310 kOe in the 4.2–300 K temperature range with special attention paid near TM0. The spontaneous magnetization at 4.2 K (3.2 μB/mol) is smaller than for YFe2D4.2 (3.7 μB/mol), showing the contribution of Gd moments. Above 110 K, metamagnetic field-induced transitions are observed: the transition field HTR increases linearly with T. These transitions exist up to 170 K. The influence of both cell volume change and Gd magnetic contribution are finally discussed in comparison with other deuterides.
    No preview · Article · Mar 2012 · Journal of Applied Physics
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    ABSTRACT: Synthesizing single phase nanocrystalline rare earth iron garnet is difficult owing due to its complex crystal structure. In this report, single phase Dy3Fe5O12 nanoparticles with different grain sizes (50, 32, and 22 nm) were prepared using the ball milling technique in a controlled atmosphere. The average grain size decreases with milling time, and reaches 22 nm after 30 h of milling. The magnetization for the as-prepared micron sized Dy3Fe5O12 is in quasi-perfect agreement with the single crystal values, and all the Fe and Dy ions are in trivalent state. When the grain size is reduced below 50 nm (10 h), the magnetization strongly depends upon the applied field, and no saturation is observed even at an applied field of 280 kOe. The compensation temperature (Tcomp) for the nanocrystalline Dy3Fe5O12 samples are a few degrees higher than that of the bulk. There is no evidence for the presence of Fe2+ charge state in the as-prepared garnets. However, Mössbauer spectroscopy studies show that about 14–15 at. % Fe2+ content was found in the 30 h (22 nm) milled sample at 77 K. Oxygen vacancies created during milling induces the presence of Fe2+ ions in the nanocrystalline Dy3Fe5O12 particles.
    No preview · Article · Feb 2012 · Journal of Applied Physics

  • No preview · Article · Nov 2010 · ChemInform
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Nov 2010 · ChemInform
  • C.V. Colin · Olivier Isnard · M. Guillot
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    ABSTRACT: The solubility limit of Ge in the YCo5−xGex structure is shown to be close to one Ge atom per formula unit by combining diffraction techniques and electron microscopy. The evolution of the crystal structure of the YCo4.5Ge0.5 compound is studied by X-ray and neutron diffraction experiments. A preferential substitution scheme is observed, the Ge atom being preferentially located on the Co 3g positions. Powder neutron diffraction results shows that the Co magnetic moments are significantly reduced by the presence of Ge in the crystal structure. The intrinsic magnetic properties such as the saturation magnetization and the magnetocrystalline anisotropy parameters are determined at 4.2 and 300 K from a fit of the isothermal magnetization curves measured in applied field up to 23 T. Ge for Co substitution induces a reduction of the first order anisotropy parameter. The large magnetocrystalline anisotropy found for YCo4.5Ge0.5 is not much reduced upon heating from 4 to 300 K. The results are compared and commented in the light of that reported earlier for YCo5 and other homologues such as YCo4Al or YCo4Ga.
    No preview · Article · Aug 2010 · Journal of Alloys and Compounds
  • M. Guillot · V. Paul-Boncour · T. Leblond
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    ABSTRACT: The study of the Y <sub>0.7</sub> Er <sub>0.3</sub> Fe <sub>2</sub>( H , D )<sub>4.2</sub> shows that the Y for Er substitution modifies both structural and magnetic properties of the hydrides and deuterides. Their cell volume is smaller than for the nonsubstituted compounds. Under high magnetic field two field-induced transitions are observed, the first one that takes place between 4.2 and 26 K (hydride) and 53 K (deuteride) originates from the erbium magnetic behavior, the second one found above 101 K (hydride) and 60 K (deuteride) is mainly attributed to an antiferro-ferromagnetic transition in the Fe sublattice. This important isotopic effect is attributed to the change of the cell volume induced by the deuterium and hydrogen insertion. Comparison with YFe <sub>2</sub> H <sub>4.2</sub> and YFe <sub>2</sub> D <sub>4.2</sub> compounds shows that the temperature at which appears the second transition is shifted to lower values. The transition field increases linearly versus temperature but with a much larger Δ H <sub> TR </sub>/Δ T slope for the deuteride compared to the hydride whereas there were similar in the nonsubstituted compounds. The roles of both cell volume change and erbium magnetic contribution are briefly discussed.
    No preview · Article · Jun 2010 · Journal of Applied Physics
  • Source
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    ABSTRACT: Here we report the single phase nanostructured Gd <sub>3</sub> Fe <sub>5</sub> O <sub>12</sub> garnets with different grain sizes (bulk, 75, 47, 35, and 22 nm) were prepared by ball milling for various milling times. Both the average grain size and the lattice parameter were estimated from the x-ray diffraction line broadening. The <sup>57</sup> F e Mössbauer spectra were recorded at 300 and 77 K for the samples with different grain sizes clearly evidenced the formation of Fe <sup>2+</sup> ions induced by milling and the content of Fe <sup>2+</sup> increases with milling time. At 4.2 K, a significant increase in saturation magnetization (+11 % ) has been observed for the 47 nm particles. The magnetization is strongly applied field dependent and no saturation effect is observed even at fields as high as of 320 kOe. The results presented here have been explained in terms of the key role played by the Fe <sup>2+</sup> ions.
    Full-text · Article · Jun 2010 · Journal of Applied Physics
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    ABSTRACT: The isothermal magnetization curves were carried out on magnetically aligned powder of the SmCo4Ga and SmCo4Al samples; they have been measured at 4.2 K in applied field up to 33 T produced by a water-cooled resistive magnet. The intrinsic magnetic properties such as saturation magnetization, anisotropy constant, and anisotropy field have been derived. Whereas some properties, such as the saturation magnetization or the Curie temperature are found to be strongly reduced upon Ga or Al for Co substitution, on the contrary the magnetocrystalline anisotropy is much larger for the substituted compounds. Hysteresis cycles are presented also and coercivity ranging from 4.5 to 6 T are reported. The mechanism at the origin of the coercivity is also modified from a nucleation type for SmCo5 to a pinning type for the Ga or Al containing compounds.
    No preview · Article · May 2010 · Journal of Applied Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Mar 2010 · ChemInform
    [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Feb 2010 · ChemInform
  • Yildirhan Oner · M. Guillot
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    ABSTRACT: Magnetization measurements have been carried out on ErCo <sub>(2-x)</sub> Ti <sub>x</sub> ( x=0 , 0.01, 0.02, 0.03, 0.04, and 0.05) alloys in the temperature range of 4–300 K under high dc magnetic fields of up to 23 T. The substitution of Ti for Co causes no change in the crystal structure of ErCo <sub>2</sub> (cubic Laves phase C15 with space group Fd 3 m ). The lattice parameter a decreases almost linearly with increasing x up to x=0.04 and then increases slightly for the largest Ti concentration. The Curie temperature T<sub>C</sub> shows a similar change with Ti concentration. Above T<sub>C</sub> all the studied samples show a small but unambiguous hysteresis associated with a metamagnetic transition. The observed hysteresis is attributed to the coexistence of the paramagnetic and the field-induced ferrimagnetic states. Linear temperature extrapolations of the critical fields H<sub>c1</sub> (where the hysteresis sets in) and H<sub>c2</sub> (the highest field where the hysteresis is observed) were done for each sample. Two different critical temperatures were found suggesting the existence of Co clusters. Indeed, weak negative magnetization values in low fields at low temperatures were observed for zero-field-cooling magnetic measurements. The negative magnetization is also attributed to the existence of Co clusters above T<sub>C</sub> . The spontaneous magnetization values M<sub>s</sub> of the samples were deduced as a function of Ti concentration from the high-field data. M<sub>s</sub> passes through a maximum for the x=0.03 sample with a maximum value of 7.15μ<sub>B</sub> (- 6.30μ<sub>B</sub> in pure ErCo <sub>2</sub> ). We show how a decrease in the Er–Co antiferromagnetic exchange coupling with Ti doping may lead to such an observed maximum.
    No preview · Article · May 2009 · Journal of Applied Physics
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    ABSTRACT: DyMn(2)D(6) has been prepared by applying high gaseous deuterium pressure on DyMn(2). This phase is isostructural with other RMn(2)D(6) (R = Y, Er) compounds and crystallizes with a K(2)PtCl(6) type structure having an ordered anion and a partially disordered cation arrangement because Dy and half the Mn atoms are randomly substituted in the same 8c site. The reverse susceptibility follows a Curie-Weiss law with an effective moment of 10 μ(B) similar to that of DyMn(2). Short range magnetic order, corresponding to ferromagnetic correlations, is observed in the neutron patterns up to 10 K and can be attributed to Dy-Dy interactions. The decomposition of the deuteride into Mn and DyD(2), studied by thermal gravimetric analysis, occurs between 470 and 650 K. A further deuterium desorption takes place above 920 K.
    No preview · Article · Jan 2009 · Journal of Physics Condensed Matter
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    ABSTRACT: Magnetization of a TbPtGe2 polycrystalline sample has been measured at a high magnetic field up to 22.5 T. The magnetization curves show a two-step metamagnetic process for the low temperature phase (below 12.5 K) and have paramagnetic character for the high temperature phase. For the low temperature phase the values of both critical fields HC1 and HC2 change slightly with increasing temperature. In the high temperature phase the critical field HC1 quickly decreases with increasing temperature. In addition, specific heat studies were performed up to magnetic fields of 9 T to confirm the magnetic phase diagram.
    No preview · Article · Aug 2008 · Solid State Communications
  • Maurice Guillot · Yildirhan Oner
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    ABSTRACT: The magnetization of powdered Mg Cu2 structure-type intermetallic Er Co1.95 Ti0.05 was studied in the temperature range of 4.2-123 K in magnetic fields up to 23 T. A field-cooled magnetization jump at certain temperatures (TC) corresponds to a first-order magnetic phase transition from a paramagnetic to a ferrimagnetic state indicating cobalt moment formation. We observe that TC approach asymptotically T=50 K with the cooling field Hc. The magnetization above TC stays constant (temperature independent), but does not saturate even in the field of 23 T. The moment per unit formula was found to be approximately 7.25 μB for this field. This behavior may be attributed to domain structures with the enhanced magnetocrystalline anisotropy field with titanium impurities. Magnetization versus magnetic field curves has also been recorded for both zero-field-cooled and field-cooled cases at various temperatures below and above TC. These curves below TC show typical ferrimagnetic phase; in the intermediate temperature range of 34-50 K metamagnetism was observed and the sample becomes pure paramagnetic above 50 K. In addition, the resistivity measurement was performed in the temperature range of 4.2-273 K. A jumplike drop in the resistivity was observed at TC. In comparison with that of Er Co2, this transition temperature shifts to higher temperature as much as 2 K, consistent with the slight increase of the lattice parameter. This drop in resistivity becomes much deeper presumably due to the internal magnetoresistance within the large domains. Analysis of the resistivity data in terms of spin fluctuations including s-d electron scattering and electron-phonon interaction reveals that T2 behavior becomes dominant in the temperature range of 34-50 K where the magnetization data exhibit metamagnetism. Therefore, we assert based on both magnetization and resistivity results that the spin-fluctuation effects are driving force for the cobalt moment formations.
    No preview · Article · May 2008 · Journal of Applied Physics
  • O. Isnard · M. Guillot
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    ABSTRACT: Hydrogen atoms insertion within the crystal structure of the RFe 11Ti compounds induces a significant modification of the physical properties. This includes an anisotropic unit cell expansion as well as a large increase of the Curie temperature. Other magnetic properties such as the magnetocrystalline anisotropy are also affected by H insertion within the lattice. The magnetic phase diagram of the TmFe11TiHx and TbFe11TiHx compounds have been investigated by combining neutron diffraction, magnetic measurements as well as high magnetic field measurements. The competition between the magnetocrystalline anisotropy terms can lead to spin reorientation phenomena in RFe11TiH with some rare-earth whereas for some others like Tb the spin reorientation transitions observed in the TbFe11Ti compounds has disappeared. In the case of the Tm compound a uniaxial character is observed up to the Curie temperature.
    No preview · Article · Apr 2008 · Journal of Optoelectronics and Advanced Materials
  • Fang Zhang · You Xu · Maurice Guillot · Jie Hui Yang
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    ABSTRACT: Based on the quantum theory, a detailed theoretical analysis of both the magnetic and magneto-optical properties of NdF3 is developed. Using the one-ion model, the choice of the crystal field parameters plays a crucial role. The reasons for the 4.2 K isothermal M(H) curve intersecting with the 1.6 K M(H) curve, and for the nonlinear relation between the Faraday rotation and the magnetic field at low temperature, are that the lowest three crystal fields and spin-orbit interaction split levels are not only split, but also strongly mixed with each other by H. Other specific properties like the magnetic susceptibility anisotropy in the 4.2-1100 K temperature range are also well interpreted.
    No preview · Article · Apr 2008 · Journal of Applied Physics
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    ABSTRACT: Magnetic properties of the dinuclear cobalt complex [Co2(ox) tpmc](ClO4)2·3H2O have been studied from the magnetization data obtained in the high magnetic field-low temperature experiments (5≤20 T, 2.2 K≤T≤29 K). An excellent agreement between experimental and calculated data for all experimental temperatures was achieved within the framework of the isolated Ising Co(II) pairs in the ground state, where each cobalt ion from the pair was situated in a differently distorted octahedral environment ("asymmetric dimer"). The obtained values for g-factors (ga and gb), and for the intracluster exchange integral J/kB = (-16.0 ±0.5) K confirm both the previous results on the crystal structure of the complex under consideration and the assumption on the strong antiferromagnetic coupling between cobalt ions realized by the superexchange interaction over the asymmetric oxalato bridge.
    No preview · Article · Nov 2007 · Revue Roumaine de Chimie
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    ABSTRACT: In this report the results of crystal structure investigations, high magnetic field measurements and electronic structure calculations carried out for the MnFe1−xCoxP system are presented. The crystal structure parameters were determined using the x-ray powder diffraction method. On this basis the inter-atomic distances were calculated and the magnetic couplings between magnetic atoms in MnFe1−xCoxP are discussed. Magnetic properties of the series of compounds with x = 0.3, 0.45, 0.5, 0.525, 0.55, 0.65 and 0.7, as determined under strong magnetic field (up to 20 T), are reported. The electronic band structure calculations were performed using the Korringa–Kohn–Rostoker method with the coherent potential approximation (KKR-CPA). The site preference of Co and Fe atoms, located in pyramidal and tetrahedral positions, was analysed and magnetic properties of Co and Fe sublattices were calculated based on total energy computations. The site-decomposed densities of states and the magnetic moment values were calculated in the whole alloy concentration range assuming a ferromagnetic (F) order. For MnFe0.35Co0.65P the KKR-CPA calculations were carried out assuming different types of antiferromagnetic (AF) arrangement in order to elucidate the origin of the AF–F transition. The magnetic interactions between transition metal atoms, as established from the phenomenological analysis of relating magnetic couplings and inter-atomic distances, were discussed based on the evolution of the site-decomposed density of states and the corresponding dependence of local magnetic moments on alloy composition. A satisfying agreement between experimental and calculated values of magnetization and local magnetic moments localized on Mn, Co and Fe sites was found.
    No preview · Article · Aug 2007 · Journal of Physics Condensed Matter
  • J. Ostoréro · M. Guillot
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    ABSTRACT: The magnetic properties of the Ho6-xYxFe23Dz (x=0, 0.5, 1 and z=0, 16) deuterides and of the parent alloys are studied under high dc magnetic field (230 kOe) on samples oriented parallel and perpendicular to the external field in the 4.2-300 K temperature range. All compounds that retain the cubic Fm3m crystallographic structure present canted ferrimagnetic structure. For most of the samples, field-induced transitions characterized by a linear variation of M above the transition field are found. Upon deuteration drastic changes of the magnetic properties are observed and the main ``magnetic parameters'' are then determined. In the alloys the exchange interaction Ho-Fe increases when the yttrium content increases but decreases in the deuterides. For all alloys the Curie temperature remains close to 510 K.
    No preview · Article · May 2007 · Journal of Applied Physics
  • J. Ostoréro · M. Guillot
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    ABSTRACT: The influence of deuteration on the magnetic properties of aluminum-substituted R6Fe23-xAlxDz compounds (R=Ho,Y; x=0,5; z=10,16) has been investigated by magnetization measurements in the temperature range of 5-350 K under a magnetic field of up to 90 kOe. In comparison to the parent alloys, a large increase of the Fe magnetic moment muFe, much larger in yttrium than in holmium compounds, is observed upon deuteration. The magnetic exchange coupling NHo-Fe between the R and Fe sublattices was estimated from the slope of the field-induced transitions of the magnetization M isotherms in the vicinity of the compensation temperature Tcomp. The values of NHo-Fe and Tcomp decrease with insertion of deuterium, indicating a weakening in R-T coupling. The different results are analyzed within the frame of the Néel ferrimagnetic model taking into account the noncolinearity of the Ho and Fe sublattices magnetizations. The Ho-Ho and Fe-Fe magnetic interactions and the canting angle theta(theta
    No preview · Article · May 2007 · Journal of Applied Physics

Publication Stats

2k Citations
394.17 Total Impact Points


  • 1978-2012
    • French National Centre for Scientific Research
      • • Laboratoire National des Champs Magnétiques Intenses
      • • Institut Néel
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • University Joseph Fourier - Grenoble 1
      • Laboratoire National des Champs Magnétiques Intenses
      Grenoble, Rhone-Alpes, France
  • 2007
    • Polish Academy of Sciences
      • Instytut Fizyki
      Warsaw, Masovian Voivodeship, Poland
  • 2002-2006
    • National High Magnetic Field Laboratory
      Tallahassee, Florida, United States
  • 1994-2004
    • Université Blaise Pascal - Clermont-Ferrand II
      • Institut de Chimie de Clermont-Ferrand
      Clermont, Auvergne, France
  • 2000
    • Cracow University of Technology
      • Institute of Physics
      Cracovia, Lesser Poland Voivodeship, Poland
  • 1988
    • Université de Rennes 1
      Roazhon, Brittany, France
    • Jagiellonian University
      Cracovia, Lesser Poland Voivodeship, Poland
  • 1976-1977
    • Laboratoire d'Informatique de Grenoble
      Grenoble, Rhône-Alpes, France