A Mössbauer spectral study of the Gd Co4-x Fex B compounds

Fernande Grandjean, Raphaël P. Hermann, E. Popiel, Gary J. Long

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Abstract

The iron-57 Mössbauer spectra of the Gd Co4-x Fex B compounds, where x is 0.10, 0.15, 0.20, 0.25, 1, 2, 2.5, and 2.6, have been measured at room temperature and reveal relatively small iron hyperfine fields of approximately 12-18 T, relatively large quadrupole interactions of approximately +0.9 and -1 mms, and three very different types of spectra for x=0.10 and 0.15, x=0.25, 1, and 2, and x=2.5 and 2.6. The differences result from both the different easy magnetization directions in these compounds and the different cobalt andor iron occupancies of the crystallographic 2c and 6i sites. The spectra have been fitted by calculating the spectral absorption with the complete iron-57 nuclear excited state Hamiltonian for the iron 2c and 6i sites. The fits have used an asymmetry parameter and Euler angles θ and φ that relate the hyperfine field to the iron electric field gradient axes of each crystallographic site in an orientation that is consistent with the structural and magnetic properties of the site. The results of the fits indicate both that the full Hamiltonian approach is required for physically reasonable spectral fits and that the small observed fields result from the presence of large orbital contributions which subtract from the Fermi contact contributions to the magnetic hyperfine fields of the two sites. The iron 2c occupancy obtained from the Mössbauer spectral area has been used to model the compositional dependence of the magnetic anisotropy constant in the Gd Co4-x Fex B compounds.

Original languageEnglish
Article number023917
JournalJournal of Applied Physics
Volume101
Issue number2
DOIs
StatePublished - 2007
Externally publishedYes

Funding

The authors thank Z. Lin and Professor O. Isnard for their help and suggestions during the course of this work. This work was partially supported by the Fonds National de la Recherche Scientifique, Belgium, through Grant No. 9.456595.

FundersFunder number
Fonds De La Recherche Scientifique - FNRS9.456595

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