G. Bouzerar

Publications (5)4.71 Total impact

• Article: Non-magnetic doping induced magnetism in Li doped SnO2 nanoparticles

  S. K. Srivastava, P. Lejay, A. Hadj-Azzem, G. Bouzerar
  [show abstract] [hide abstract]
  ABSTRACT: We address the possibility of non-magnetic doping induced magnetism, in Li doped SnO2 nano-particles. The compounds have been prepared by solid state route at equilibrium and were found to be crystallized in single rutile phase. The magnetization measurements have shown that Li-doping induces magnetism in SnO2 for a particular range of Li concentration. However, for other Li concentrations, including pure SnO2, the samples exhibit diamagnetism. To investigate the possible origin of the induced magnetism, we have studied the variation of the magnetization as a function of the average nano-particle radius. Possible scenarios for the appearance of magnetism in these compounds are discussed.
  02/2013;
• Article: Non-magnetic impurity induced magnetism in rutile TiO2:K compounds.

  S K Srivastava, P Lejay, B Barbara, O Boisron, S Pailhès, G Bouzerar
  [show abstract] [hide abstract]
  ABSTRACT: Recent ab initio studies have theoretically predicted room temperature ferromagnetism in several oxide materials of the type AO(2) in which the cation A(4+) is substituted by a non-magnetic element of the 1 A column. Our purpose is to address experimentally the possibility of magnetism in Ti(1-x)K(x)O(2) compounds. The samples have been synthesized via the solid state route method at equilibrium. Our study has shown that Ti(1-x)K(x)O(2) is thermodynamically unstable and leads to a phase separation, in contradiction with the hypothesis of ab initio calculations. In particular, the crystalline TiO(2) grains appear to be surrounded by K-based phase. The oxidization state of the Ti ion is found to be in Ti(4+) as confirmed from the x-ray photoelectron spectra measurement. Nevertheless, K:TiO(2) compounds exhibit weak paramagnetism with the highest magnetic moment of ~0.5 μ(B) K(-1) but no long-range ferromagnetic order. The observed moment in these compounds remains much smaller than the predicted moment of 3 μ(B) by ab initio calculation. The apparent contradictions between our experiments and first-principles studies are discussed.
  Journal of Physics Condensed Matter 11/2011; 23(44):442202. · 2.55 Impact Factor
• Article: Absence of ferromagnetism in Mn-doped tetragonal zirconia

  S. K. Srivastava, P. Lejay, B. Barbara, O. Boisron, S. Pailhes, G. Bouzerar
  [show abstract] [hide abstract]
  ABSTRACT: In a recent letter, it has been predicted within first principle studies that Mn-doped ZrO 2 compounds could be good candidates for spintronics application because expected to exhibit ferromagnetism far beyond room temperature. Our purpose is to address this issue experimentally for Mn-doped tetragonal zirconia. We have prepared polycrystalline samples of Y 0.15 (Zr 0.85-y Mn y )O 2 (y = 0, 0.05, 0.10, 0.15, 0.20) by using standard solid state method at equilibrium. The obtained samples were carefully characterized by using x-ray diffraction, scanning electron microscopy, elemental color mapping, x-ray photoemission spectroscopy, and magnetization measurements. From the detailed structural analyses, we have observed that the 5% Mn doped compound crystallized into two symmetries (dominating tetragonal and monoclinic), whereas higher Mn doped compounds are found to be in the tetragonal symmetry only. The spectral splitting of the Mn 3s core-level x-ray photoelectron spectra confirms that Mn ions are in the Mn³⁺ oxidation state and indicate a local magnetic moment of about 4.5 μ B /Mn. Magnetic measurements showed that compounds up to 10% of Mn doping are paramagnetic with antiferromagnetic interactions. However, higher Mn doped compound exhibits local ferrimagnetic ordering. Thus, no ferromagnetism has been observed for all Mn-doped tetragonal ZrO 2 samples.
  Journal of Applied Physics 09/2011; · 2.17 Impact Factor
• Source

  Available from: ArXiv

  Article: Is room temperature ferromagnetism possible in K-doped SnO2?

  S. K. Srivastava, P. Lejay, B. Barbara, S. Pailhès, V. Madigou, G. Bouzerar
  [show abstract] [hide abstract]
  ABSTRACT: Ab initio studies have theoretically predicted room temperature ferromagnetism in crystalline SnO2, ZrO2 and TiO2 doped with non magnetic element from the 1A column as K and Na. Our purpose is to address experimentally the possibility of magnetism in both Sn1-xKxO2 and Sn1-xCaxO2 compounds. The samples have been prepared using equilibrium methods of standard solid state route. Our study has shown that both Sn1-xCaxO2 and Sn1-xKxO2 structure is thermodynamically unstable and leads to a phase separation, as shown by X-ray diffraction and detailed micro-structural analyses with high resolution transmission electron microscopy (TEM). In particular, the crystalline SnO2 grains are surrounded by K-based amorphous phase. In contrast to Ca: SnO2 samples we have obtained a magnetic phase in K: SnO2 ones, but no long range ferromagnetic order. The K: SnO2 samples exhibit a moments of the order of 0.2 {\mu}B/K /ion, in contrast to ab-initio calculations which predict 3{\mu}B, where K atoms are on the Sn crystallographic site. The apparent contradictions between our experiments and first principle studies are discussed.
  04/2010;
• Article: Possible room-temperature ferromagnetism in K-doped SnO_ {2}: X-ray diffraction and high-resolution transmission electron microscopy study

  S. K. Srivastava, P. Lejay, B. Barbara, S. Pailhès, V. Madigou, G. Bouzerar
  [show abstract] [hide abstract]
  ABSTRACT: Ab initio studies have theoretically predicted room-temperature ferromagnetism in crystalline SnO2, ZrO2, and TiO2 doped with nonmagnetic element from the 1A column as K and Na. Our purpose is to address experimentally the possibility of magnetism in both Sn1−xKxO2 and Sn1−xCaxO2 compounds. The samples have been prepared using equilibrium methods of standard solid-state route. Our study has shown that both Sn1−xCaxO2 and Sn1−xKxO2 structure is thermodynamically unstable and leads to a phase separation, as shown by x-ray diffraction and detailed microstructural analyses with high-resolution transmission electron microscopy. In particular, the crystalline SnO2 grains are surrounded by K-based phase. In contrast to Ca:SnO2 samples, we have obtained a magnetic phase in K:SnO2 ones but no long-range ferromagnetic order. The K:SnO2 samples exhibit a moment on the order of 0.2 μB/K /ion, in contrast to ab initio calculations which predict 3 μB, where K atoms are on the Sn crystallographic site. The apparent contradictions between our experiments and first-principles studies are discussed.
  Phys. Rev. B. 82(19).