Superconductivity in heavy-fermion U(Pt,Pd)3 and its interplay with magnetism

Abstract

The effect of Pd doping on the superconducting phase diagram of the unconventional superconductor UPt3 has been measured by (magneto)resistance, specific heat, thermal expansion, and magnetostriction. Experiments on single- and polycrystalline U(Pt1−xPdx)3 for x<~0.006 show that the superconducting transition temperatures of the A phase Tc+, and of the B phase Tc− both decrease, while the splitting ΔTc increases at a rate of 0.30±0.02K/at.% Pd. The B phase is suppressed first, near x=0.004, while the A phase survives until x≅0.007. We find that ΔTc(x) correlates with an increase of the weak magnetic moment m(x) upon Pd doping. This provides further evidence for Ginzburg-Landau scenarios with magnetism as the symmetry-breaking field, i.e., the two-dimensional (2D) E representation and the 1D odd-parity model. Only for small splittings ΔTc∝m2(Tc+) (ΔTc<~0.05K) as predicted. The results at larger splittings call for Ginzburg-Landau expansions beyond fourth order. The tetracritical point in the B-T plane persists until at least x=0.002 for B⊥c, while it is rapidly suppressed for B∥c. Upon alloying the A and B phases gain stability at the expense of the C phase.

Source-reported materials — not catalogue approval

Similar papers