Título
Upper critical fields in a FeSeO.5TeO.5 superconducting single crystal
Autor
DIEGO VELASCO SOTO
Colaborador
FRANCISCO JAVIER RIVERA GOMEZ (Colaborador)
CARLOS ROBERTO SANTILLAN RODRIGUEZ (Colaborador)
JOSE ANDRES MATUTES AQUINO (Colaborador)
Nivel de Acceso
Acceso Abierto
Materias
Resumen o descripción
A single crystal with a nominal composition FeSe0.5Te0.5 was obtained by the Bridgman method. A
quartz ampulla with the sample inside was vacuum-sealed and maintained at 1050 !C for 37 h to
homogenize the sample. Subsequently, the quartz ampulla with the sample was moved with a
speed of 2.2 mm/h to a furnace which was at 450 !C. X-ray diffraction confirmed the tetragonal
structure of the grown single crystal with the cleavage plane corresponding to the ab plane.
Resistance measurements were carried out with magnetic fields from 0 to 9 T, applied parallel to
the c axis and ab plane, respectively. A zero-field critical temperature Tc¼14K was determined.
The upper critical field vs. temperature phase diagram was built for temperatures where the
resistance drops to 90%, 50%, and 10% of the normal state resistance. The linear extrapolation to
T¼0K gave upper critical fields of 57.2, 51.8, and 46.0 T for Hjjc axis and 109.6, 95.5, and 80.9 T
for Hjjab. Applying the Werthamer–Helfand–Hohenberg (WHH) theory, upper critical fields of
39.6, 35.9, and 31.8 T and coherence lengths of 28.8, 30.3, and 32.1A ° were obtained for Hjjc;
while for Hjjab, upper critical fields of 51.3, 40.7, and 37.5 T and coherence lengths of 22.3, 26.7,
and 31.5A ° were obtained. The value of l0Hc2/kBTc calculated by the WHH theory exceeds the
Pauli limit (1.84 T/K) indicating the unconventional nature of superconductivity. The activation
energy U0 has two different rates of change with the applied magnetic field probably due to two
different thermal activation mechanisms; the origin of which requires further investigation. A
similar behavior is observed in the irreversibility lines.
Fecha de publicación
marzo de 2013
Tipo de publicación
Artículo
Versión de la publicación
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Fuente de Objetos Científicos Open Access
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