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57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4

(2009)
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Abstract
Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice. In order to gain some insight in this controversial problem, a 57Fe Mössbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field Mössbauer spectra. In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass. From the Mössbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment. Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram.

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Citation

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Chicago
Alakrmi, Abdurazak. 2009. “57Fe Mössbauer Spectroscopic Study of the Spin-glass Transitions in the Mixed Spinel Series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4”. Ghent, Belgium: Ghent University. Faculty of Sciences.
APA
Alakrmi, A. (2009). 57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4. Ghent University. Faculty of Sciences, Ghent, Belgium.
Vancouver
1.
Alakrmi A. 57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4. [Ghent, Belgium]: Ghent University. Faculty of Sciences; 2009.
MLA
Alakrmi, Abdurazak. “57Fe Mössbauer Spectroscopic Study of the Spin-glass Transitions in the Mixed Spinel Series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4.” 2009 : n. pag. Print.
@phdthesis{811761,
  abstract     = {Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice.
In order to gain some insight in this controversial problem, a 57Fe M{\"o}ssbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field M{\"o}ssbauer spectra.
In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass.
From the M{\"o}ssbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment.
Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram.},
  author       = {Alakrmi, Abdurazak},
  language     = {eng},
  pages        = {VI, 114},
  publisher    = {Ghent University. Faculty of Sciences},
  school       = {Ghent University},
  title        = {57Fe M{\"o}ssbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4},
  url          = {http://lib.ugent.be/fulltxt/RUG01/001/369/720/RUG01-001369720\_2010\_0001\_AC.pdf},
  year         = {2009},
}