Abstract
Pressure effects on superconducting properties of two samples and 7.5 K) were investigated by measurements of electrical resistivity, magnetic susceptibility, and x-ray diffraction in the pressure range up to 320 kbar. Magnetoresistivity measurements down to 60 mK and up to 47 kbar have shown a negative pressure effect on as well as on the third critical field with the slopes /kbar and /kbar, respectively. The magnetic susceptibility measurements evidenced that the slope of gradually decreases with pressure reaching a value three times smaller at 112 kbar. The lattice parameter measurements revealed the volume reduction of 14% at 320 kbar. The pressure-volume dependence is described by the Rose-Vinet equation of state. The obtained relative volume dependence analyzed by the McMillan formula for indicates that the reduction of the superconducting transition temperature is mainly due to hardening of the Einstein-like phonon mode responsible for the superconducting coupling. This is confirmed by the analysis of the resistivity measurements in the normal state up to K performed at pressures up to 28 kbar.
- Received 20 May 2014
- Revised 8 July 2014
DOI:https://doi.org/10.1103/PhysRevB.90.045136
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