High-pressure effect on the superconductivity of YB₆

    Pressure effects on superconducting properties of two YB₆ samples (T_c = 5.9 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 T_c as well as on the third critical field Hc3 with the slopes dlnT_c/dp = -0.59%/kbar and dlnH_c3/dp = -1.1%/kbar, respectively (Fig. 1). The magnetic susceptibility measurements evidenced that the slope of dlnT_c/dp gradually decreases with pressure reaching a value three times smaller at 112 kbar (Fig. 2). The lattice parameter measurements revealed the volume, V, reduction of 14% at 320 kbar (Fig. 3). The obtained relative volume dependence lnT_c vs lnV analyzed by the McMillan formula for T_c 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 with the “thermal spectroscopy” by the analysis of the resistivity in the normal state at various pressures (Fig. 4 and Fig. 5).

S. Gabáni, I. Takáčová, G. Pristáš, E. Gažo, K. Flachbart, T. Mori, D. Braithwaite, M. Míšek, K.V. Kamenev, M. Hanfland and P. Samuely:
High-pressure effect on the superconductivity of YB₆,
Physical Review B 90, 045136 (2014).
 

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