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Increase in the superconducting transition temperature in Zr-Hf alloys due to $s-d$ electron transfer under pressure
I. O. Bashkin,
M. V. Nefedova,
E. G. Ponyatovskii,
V. G. Tissen Institute of Solid State Physics, Russian Academy of Sciences
Abstract:
The superconducting transition temperatures
$T_c$ of Zr-Hf alloys are measured as a function of pressure up to 47.4 GPa. It is found that the value of
$T_c$ experiences jumps due to the transition of the hexagonal
$\omega$ phase to the
$\beta$ phase:
$T_c$ of the Zr
$_{80}$Hf
$_{20}$ alloy increases from 3.2 to 11 K at
$P=35.0$ GPa, and a jump in
$T_c$ from 3.4 to 10 K is observed for the Zr
$_{67}$Hf
$_{33}$ alloy at
$P=40.9$ GPa. The isobars of the concentration dependence
$T_c(c)$ of the bcc Zr-Hf alloys are qualitatively similar to the
$T_c(c)$ curves for the bcc phases in the systems of V
$b$–IV
$b$ subgroup elements at
$P=1$ atm. The data obtained indicate that, because of the
$s-d$ electron transition, the IV
$b$ subgroup metals become similar in their crystal structure and superconducting properties to the V
$b$ subgroup metals.
PACS:
64.70.Kb,
74.62.-c Received: 23.06.2003
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