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.