M. Guillot

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

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Publications (185)326.53 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.
    Journal of Applied Physics 03/2012; 111(7). · 2.21 Impact Factor
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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.
    Journal of Applied Physics 06/2010; · 2.21 Impact Factor
  • C.V. Colin, O. 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.
    Journal of Alloys and Compounds 01/2010; 505(1):11-16. · 2.73 Impact Factor
  • ChemInform 01/2010; 26(45).
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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.
    Journal of Applied Physics 01/2010; 107. · 2.21 Impact Factor
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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.
    Journal of Physics Condensed Matter 01/2009; 21(1):016001. · 2.22 Impact Factor
  • 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.
    Journal of Applied Physics 01/2008; 103. · 2.21 Impact Factor
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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.
    Journal of Physics Condensed Matter 08/2007; 19(37):376201. · 2.22 Impact Factor
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    ABSTRACT: Recently, increasing interest has focused on DMS materials in which Mn is replaced by other transition metal ions: iron and cobalt. In Section 2 we will present particularly interesting properties of HgSe:Fe, connected with the peculiar energy position of d-derived Fe states in its band structure. Section 3 will be devoted to description of some optical and magnetic properties of Cd1-xFex Te. The Jahn-Teller coupling piays an important role in the explanation of the observed effects. In Section 4 we will discuss some result for Co-based DMS. Finally, the study of Fe2+ in lowered symmetry environment, which is realized in alloys like (Cd1-xFex)(Te1-ySey), will be presented in Section 5.
    Physica Scripta 01/2007; 1991(T39):119. · 1.03 Impact Factor
  • 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.
    Journal of Applied Physics 01/2007; 101. · 2.21 Impact Factor
  • Maurice Guillot, Fang Zhang, You Xu, Jie Hui Yang, Xing Wei
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    ABSTRACT: The magnetic and magneto-optical properties of the paramagnetic Nd3Ga5O12 crystal including the magnetic susceptibility, the magnetization, and circular magnetic birefringence (Faraday rotation) in a large wavelength range under high magnetic field were analyzed within the framework of the one-ion model. H was along the [111] cubic direction in the 4.2-300 K temperature range. A good simulation of all the available experimental results is obtained considering spin-orbit coupling, the crystal field interaction, and the Zeeman effect. The high-order correction of the Zeeman effect plays a very important role. This explains why no saturation of M and of Faraday rotation (FR) happens at very low temperatures even when H is above 30 T. The main conclusion drawn from our calculation is that the magneto-optical coefficient (Verdet constant divided by magnetic susceptibility) presents a linear variation versus the reciprocal temperature in the 70-300 K range. In other words the first-order magneto-optical effect (FR or circular magnetic birefringence) is not proportional to the magnetization.
    Journal of Applied Physics 01/2007; 101. · 2.21 Impact Factor
  • 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
    Journal of Applied Physics 01/2007; 101. · 2.21 Impact Factor
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    ABSTRACT: The Tb for Y substitution in YFe2D4.2 leads to an increase of cell volume, a canted ferrimagnetic structure at low temperature, and a shift of the magnetovolumic transition temperature to higher value. The study of the structural and magnetic properties of TbFe2H4.2 and TbFe2D4.2 indicates a significant (H,D) isotope effect implying a larger cell volume and a higher transition temperature for the hydride compared to the deuteride.
    Journal of Applied Physics 01/2007; 101. · 2.21 Impact Factor
  • Jiehui Yang, You Xu, Fang Zhang, Maurice Guillot
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    ABSTRACT: The effects of the spin–orbit (SO) interaction strength of the ground and excited configurations of rare-earth ions on the paramagnetic and diamagnetic Faraday rotation (FR) spectra in Ce-substituted yttrium iron garnets (YIG) are studied on the basis of quantum theory. It is found that the effect of the SO interaction strength of the ground configuration is stronger than the corresponding effect of the excited configuration. The reasons for this difference have been analysed in connection with the analysis of the large FR effect in Bi-substituted YIG.
    Journal of Physics Condensed Matter 09/2006; 18(40):9287. · 2.22 Impact Factor
  • Source
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    ABSTRACT: A new phase of ErMn2D6 has been prepared by applying high hydrogen pressure on C14 ErMn2. This phase is isostructural to YMn2D6 and crystallizes with a K2PtCl6 type structure having an ordered anion and a partially disordered cation arrangement as Er and half the Mn atoms are randomly substituted in the same 8c site. This hydride is very stable and decomposes into ErD2 and Mn at about 630 K. The reverse susceptibility follows a Curie–Weiss law with an effective moment of 10 μB similar to that of ErMn2. Although a saturation magnetization of 5 μB is measured at 4.2 K, smaller than that of ErMn2 (8 μB), no long range magnetic order is observed in the neutron patterns. Short range magnetic order, corresponding to both ferromagnetic and antiferromagnetic correlations, is observed in the neutron patterns up to 5 K. The chemical disorder of Er and Mn atoms on the 8c site should prevent the long range magnetic order and favour a distribution of Er spin orientation.
    Journal of Physics Condensed Matter 06/2006; 18(27):6409. · 2.22 Impact Factor
  • J. Ostoréro, M. Guillot
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    ABSTRACT: Magnetic properties of Ho6Fe23-xAlx compounds (x=0, 2.5, and 5) are reported in the temperature range of 5-550 K under a magnetic field of up to 90 kOe. A large decrease of the Curie temperature is obtained (-20 K per Al atom) as in Y6Fe23-xAlx. The compensation temperature varies from 185 K (x=0) to 280 K (x=5); it is associated with a strong increase of low-temperature spontaneous magnetization (+2.3 muB per Al atom). In the vicinity of Tcomp field-induced transitions are observed for x=0 and x=2.5. The different results are analyzed within the frame of the Néel ferrimagnetic model: the Ho-Fe and Fe-Fe magnetic interactions and the canting angle are then determined. The presence of the rare-earth Ho ``stabilizes'' the ferrimagnetism.
    Journal of Applied Physics 01/2006; 99. · 2.21 Impact Factor
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    ABSTRACT: The influence of the (H,D) isotope substitution on the metamagnetic transition in (Y1-xRx)Fe2(H1-yDy)4.2 (R=Tb, Er, x=0, 0.1, and y=0, 1) compounds has been studied by x-ray diffraction and magnetic measurements. All these compounds crystallize in the same monoclinic structure with larger cell volume for the hydrides compared to the deuterides. The metamagnetic transition temperature TM is not only field dependent but also strongly related to the volume change. The increase of TM is more strongly related to the (H,D) isotope substitution than by the rare earth substitution on the Y site.
    Journal of Applied Physics 01/2006; 99. · 2.21 Impact Factor
  • O. Isnard, M. Guillot
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    ABSTRACT: Nd2Fe17Hx compounds are investigated by high-field magnetization measurements performed up to 230 kOe in the 4.2–300-K temperature range. It is shown that the magnetic properties of the Nd2Fe17Hx (x = 1, 1.5, 2, 3, 4.9) compounds are very sensitive to the hydrogen content. Insertion of hydrogen within the crystal structure induces a large increase in the Curie temperature. The saturation magnetization is also very sensitive to the hydrogen content, but exhibits a peculiar behavior depending on the hydrogen content. The first-order anisotropy parameter decreases continuously when the hydrogen content increases. A metamagnetic field-induced transition is observed for four Nd2Fe17Hx hydrides corresponding to x = 1, 1.5, 2, 3. This metamagnetic transition manifests itself by a step in the magnetization curves recorded when the field is perpendicular to the alignment direction. The temperature dependence of the field at which the transition occurs is determined for all the studied compounds. The thermal evolution of this metamagnetic transition as well as its evolution versus the hydrogen content has been determined. The field-induced transition remains present up to temperatures close to 250–300 K.
    Journal of Applied Physics 08/2005; 98(3):033912-033912-6. · 2.21 Impact Factor
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    ABSTRACT: Magnetic measurements were performed on Yb <sub>3</sub> Fe <sub>5-x</sub> Sc <sub>x</sub> Fe <sub>5</sub> O <sub>12</sub>( YbIG : Sc ) , x=0.5 , single crystal platelets oriented along and perpendicular to the [111] crystallographic direction, in the 1.5–20 K temperature range in a magnetic field up to 330 kOe. Along the [110] and [100] axis H was limited to 230 kOe in the 4.2–300 K range. When H is parallel to [111] and [110] a first-order field induced transition are observed below about 10 K; the temperature variations of the transition field are very different. When H is applied along [100] a monotonous behavior is simply found. A noticeable anisotropy between the magnetic properties of the three samples remains present up to about 100 kOe. For the [111] sample the saturation is attained under 250 kOe below 10 K; the magnetic moment per Yb <sup>3+</sup> ion that is deduced to be 1.78±0.05 Bohr magneton confirms the strong quenching of the orbital moment by the crystalline field. In the intermediary field range (≈100–220 kOe ) , there exists no more magnetic anisotropy. The magnetization that is proportional to the applied H is characterized by the onset of a field-induced magnetic structure; the Yb–Fe exchange constant is then determined. When H lies in the (111) plane, a strong M reduction is noted in the whole H domain; however, the transition field, the linear H Yb–Fe variation domain and the saturation field are the same as along the [111] direction.
    Journal of Applied Physics 06/2005; · 2.21 Impact Factor
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    ABSTRACT: The deuterium order–disorder and the first order magnetic transitions in YFe2D4.2 have been studied by X-ray and neutron diffraction, magnetization measurements and Fe57 Mössbauer spectroscopy. From 363 down to 290 K, a progressive lowering of the crystal symmetry from cubic to rhombohedral and then monoclinic structure is observed. At 290 K YFe2D4.2 crystallizes in a primitive monoclinic space group P1c with a=9.429(1) Å, b=11.474(1) Å, c=5.508(1) Å, β=122.37°. This lowering of crystal symmetry leads to very different quantity of D neighbours around each Fe sites. The magnetic study shows that the moment of the Fe3 atoms, surrounded by nearly 5 D atoms, collapses at 84 K, leading to a transition from a ferromagnetic to an antiferromagnetic structure. The first order transition at 84 K is associated with a 0.55% volume decrease and the magnetization curves above 84 K display the same behaviour than the collective electron metamagnetism (CEM) observed in RCo2 compounds. This is related to the fact that for critical deuterium content between 4 and 5 D atoms in YFe2 the Fe 3d ferromagnetism becomes instable due to a strong modification of the electronic band structure.
    Journal of Alloys and Compounds 01/2005; 404:355-359. · 2.73 Impact Factor

Publication Stats

499 Citations
326.53 Total Impact Points

Institutions

  • 1978–2012
    • French National Centre for Scientific Research
      • • Institut Néel
      • • Laboratoire National des Champs Magnétiques Intenses
      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
  • 1997–2001
    • Nanjing University
      • Department of Physics
      Nanjing, Jiangsu Sheng, China
  • 1995
    • Institute of Nuclear Physics
      Cracovia, Lesser Poland Voivodeship, Poland
  • 1994
    • Université Blaise Pascal - Clermont-Ferrand II
      • Institut de Chimie de Clermont-Ferrand
      Clermont-Ferrand, Auvergne, France
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
  • 1993
    • Cracow University of Technology
      • Institute of Physics
      Kraków, Lesser Poland Voivodeship, Poland
  • 1976–1977
    • Laboratoire d'Informatique de Grenoble
      Grenoble, Rhône-Alpes, France