Tcand its pressure dependence for technetium-based h.c.p. solid solution alloys

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Abstract
The superconducting transition temperature Tc has been determined for a number of technetium-based h.c.p. solid solution alloys. Additions of V, Nb and Mo raise Tc whereas Co, Ni, Ru, and, in particular, Cr and Fe lower Tc relative to pure technetium. The general trend of Tc with the electron per atom ratio is consistent with that expected for a simple dependence on a rigid-band density of states, with the exception of that for the Cr and Fe alloys. An analysis of the data for these latter alloys in the context of the theory due to Kaiser (J. Phys. C., vol.3, p.410, 1970) would suggest that the enhanced depression of Tc is due to the formation of a nonmagnetic resonance state. The hydrostatic pressure dependence of Tc has been investigated up to 25 kbar with particular attention given to the h.c.p. region of the Mo-Tc-Ru system. The observed variation of delta Tc/ delta P is discussed in relation to current theoretical models.