Book/Report

FZJ-2018-02767

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Elektronische Struktur und Supraleitung von divalenten Metallen unter sehr hohem Druck

Bireckoven, B. (Corresponding author)FZJ*

1987
Kernforschungsanlage Jülich, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/18403

Report No.: Juel-2129

Abstract: A single crystal, high-pressure diamond cell has been developed for the study of superconductors under pressures to over 50 GPa. The pressure distribution in the cell (200 $\mu$m in diameter) is obtained by the ruby fluorescence technique, where the exciting laser beam can be focussed into a spot of 6 Am in diameter. A highsensitivity AC-SQUID magnetometer has been employed to detect the diamagnetic response of the very small samples at T$_{c}$. The T$_{c}$(p)-dependence of the lead-manometer has been calibrated against the ruby-pressure-scale up to pressures of 30 GPa. In spite of the well-known fcc/hcp-transition at 13 GPa lead shows a smooth T$_{c}$(p)-behaviour and thus is a very suitable manometer. Band structure calculations for the alkaline earth metals indicate an appreciable s-to-d transfer with increasing pressure. In fact, superconductivity was previously observed in the pressure induced d-transition metals Sr and Ba (however not yet in Ca). For the first time we present a quantitative investigation of T$_{c}$ as a function of p up to 50 GPa. Both elements turn out to be "good" superconductors featuring T$_{c}$'s of about 7 K. The possibility of a generalized phase diagram for the alkaline earth metals will be critically discussed. At any rate, the occurrence of such high T$_{c}$'s is rather strong evidence for a substantial d-transition metal character at high p. Investigations of very dilute $\underline{Ba}$Eu-alloys up to 45 GPareveal a strong, monotonic increase of $\Delta T_{c} = T_{c}^{Ba}-T_{c}^{BaEu}$. The strong increase of the pairbreaking behaviour in the magnetic Eu-ions may hint at a valence instability of the 4f$^{7}$-configuration towards 4f$^{6}$ under high pressure.

---

Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

---

Database coverage:

---