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

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

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Fuente de Objetos Científicos Open Access

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