INVESTIGADORES
PASQUEVICH Gustavo Alberto
congresos y reuniones científicas
Título:
Experimantall design and quantitative analysis of Mössbauer scans
Autor/es:
F. H. SÁNCHEZ; G. A. PASQUEVICH; P. MENDOZA ZÉLIS; A. VEIGA; N. MARTINEZ; M. B. FERNÁNDEZ VAN RAAP
Lugar:
Montpellier
Reunión:
Conferencia; International Conference on the Application of the Mössbauer Effect; 2005
Resumen:
Soon after the discovery of the Mössbauer effect, thermal scans performed at a fixed Doppler energy (usually zero energy) were explored in order to rapidly obtain information on magnetic ordering and other characteristic temperatures[1-3]. Nonetheless, to our knowledge, no attempts to formalize this methodology as a fully quantitative analytical tool were carried out until very recently. In this contribution, we present experiments which were chosen to demonstrate the usefulness of fixed energy scans, when are performed at especially chosen Doppler velocities and appropriately combined with Mössbauer spectroscopy. They include the study of the temperature dependence at Fe sites of the hyperfine magnetic field in FeSn2 and Fe3Si, of the quadrupole splitting in FeSi, and the study of the kinetics of the nano-crystallization process in an amorphous finemet-precursor alloy, employing the 14.4 keV transition of 57Fe. The experimental setup is presented. For data analysis, expressions of the thermal dependence of Mössbauer-Lamb factors, second order Doppler shift, hyperfine fields, etc., were explicitly included in the integral expression of the Mössbauer absorption. The integral expression was needed in order to describe appropriately the variation with temperature of saturation effects due to overlapping of gamma ray absorption cross sections. In the final part, a couple of new on going experiments is presented. One is devoted to the study of magnetic dynamic properties at a specific Fe site by recording the Mössbauer absorption at constant temperature and at a fixed Doppler energy (associated with that Fe site) while cycling an external magnetic field at various frequencies between 1 and 1000 Hz. The other is an “intelligent” following up of a Mössbauer resonance line as a function of an external parameter, such as temperature, field, etc.. [1] U. Gonser, C.J. Meechan, A.H. Muir, H. Wiedersich, J. Appl. Phys. 34 (1963) 2373. [2] H.-J. Wagner, U. Gonser, J. Magn. Magn. Mater. 31– 34 (1983) 1343. [3] C.L. Chien, Phys. Rev. B 18 (1978) 1003. [4] P. Mendoza Zélis, G.A. Pasquevich, F.H. Sánchez, N. Martínez, A. Veiga, Phys. Lett. A 298 (2002) 55.