Substitution studies and the nature of superconductivity inUPt3

The influence of Gd and Ni impurities on the superconducting transition temperature of UPt3

“…The superconducting transition temperature T~ + is determined by taking the average of the temperatures at which the resistivity has dropped by 10% and 90%. TJ as well as po vary linearly with Gd content: dTJ/dx = --0.62 K/at% Gd and dpo/dx = 13.5 I1~ cm/ Th [1]. Surprisingly, the data for Gd follow closely the results reported for non-magnetic Y and Th impurities [1], which is in strong contrast to the behaviour observed for normal BCS superconductors.…”

“…The superconducting properties of heavy-fermion UPt3 are extremely sensitive to substitutions on both the U and Pt sites [1,2]. All impurity studies reported so far were directed towards non-magnetic elements: Y and Th doping on the U site, and Pd, Ir and Au doping on the Pt site.…”

“…All impurity studies reported so far were directed towards non-magnetic elements: Y and Th doping on the U site, and Pd, Ir and Au doping on the Pt site. Electrical resistivity and specific-heat experiments [ 1,2] yielded firm evidence that non-magnetic impurities do not simply give rise to pair-weakening, but rather give rise to effects comparable to pair-breaking, which is in strong contrast to the standard behaviour for ordinary BCS singlet superconductors. This suggests that nonmagnetic impurities act as holes in the Kondo-lattice.…”

Low-temperature phase diagram of the heavy-fermion superconductor UPt3

“…12 Substitution studies result in all cases in a fast depression of superconductivity with, in case of Pd substitutions, an appreciable increase 177 0022-2291/94/0400-0177507.00/0 9 1994 Plenum Publishing Corporation of the distance in temperature between the two superconducting transitions. 7 On the other hand, at further increasing the Pd concentration to two percent or more, superconductivity is lost and long-range antiferromagnetic order is found with magnetic moments of 0.5 #B per formula unit. 13 These observations suggest a relation between the intensity of the splitting and the magnetic-moment formation in the Pd-substituted alloys and are in line with the existence of a critical uniaxial pressure along the c-axis above which the splitting and the weak moment disappear.…”

Sb-NQR Probe for Multiband Superconductivity in Filled-Skutterudite Compounds (Pr1-xLax)Os4Sb12

“…8 This result is in contrast with the well known fact that the unconventional HF superconductors undergo a marked depres-sion of T c by substituting La for Ce which eliminates the 4f -electrons derived coherence effect in pure compounds. [12][13][14] In this paper, we report on the intimate evolution of electronic and SC characteristics in a series of (Pr 1−x La x )Os 4 Sb 12 compounds through the Sb-NQR measurements.…”