Volume 77, Number 4, February 2007
Article Number 43001
Number of page(s) 4
Section Atomic, Molecular and Optical Physics
Published online 09 February 2007
EPL, 77 (2007) 43001
DOI: 10.1209/0295-5075/77/43001

Structural characterization of the $\chem{Zr_{4} Al_{3}}$ and $\chem{Hf_{4} Al_{3}}$ compounds by means of hyperfine interaction studies

P. Wodniecki1, 2, A. Kulinska1, 2, B. Wodniecka1, S. Cottenier3, 4, H. M. Petrilli4, M. Uhrmacher2 and K. P. Lieb2

1  IFJ PAN, 31-342 Krakow, Poland
2  II. Physikalisches Institut, Universität Göttingen - Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
3  Instituut vor Kern- en Stralingsfisica, K. U. Leuven - Celestijnenlaan 200 D, B-3001 Leuven, Belgium
4  Instituto di Fisica, Universidade de Sao Paulo - CP 66318, 05315-970, Sao Paulo, SP, Brazil

received 10 November 2006; accepted in final form 20 December 2006; published February 2007
published online 9 February 2007

Electric-field gradients have been measured in the isostructural intermetallic compounds ${\rm Zr}_{4}{\rm Al}_{3}$ and ${\rm Hf}_{4}{\rm Al}_{3}$, using radioactive $^{181}{\rm Hf}/^{181}$Ta hyperfine probes. In both compounds, two well-defined electric-field gradients have been observed, whose temperature dependence follows the T3/2 rule in the temperature range 30$\hbox{--} $1170 K. Using the full-potential augmented plane-wave + local-orbitals formalism, the electric-field gradients have been calculated. On the basis of the 181Ta hyperfine interaction parameters, the possible Hf/Zr lattice sites have been assigned. In this way the controversy concerning the lattice structure of these compounds deduced from X-ray diffraction has been solved.

31.30.Gs - Hyperfine interactions and isotope effects, Jahn-Teller effect.
61.18.-j - Other methods of structure determination.
61.72.-y - Defects and impurities in crystals; microstructure.

© Europhysics Letters Association 2007