Magnetic Pair-Breaking in Y1−xHoxNi2B2C(x = 0, 0.25, 0.5, 0.75) Single Crystals

Abstract

Temperature-dependent resistivity and magneticsusceptibility were studied for quaternary borocarbide intermetalliccompounds Y1−xHoxNi2B2C (x = 0, 0.25,0.5, 0.75), which show coexistence of superconductivity with magnetism.In a normal state, the compounds exhibit conventional metallicbehaviour. The Debye temperature θD is derived by fittingthe temperature dependence of resistivity to the Bloch–Gruneisenexpression, i.e. θD scales with M−0.5 (M is theaveraged atomic mass on the Y3+ site), which meansthat the acoustic mode of the lattice vibrating spectrum is influencedby the Y3+ site atoms. Fitting the temperature-dependentmagnetic susceptibility above TN to the Curie–Weiss law,effective magnetic moment μeff is deduced, and thende Gennes factor dG is calculated. It is found that as Ho contentincreases, μeff as well as dG increases and TCdecreases. Moreover, the decrease of TC scaleswith dG, i.e., ΔTC∝−nI2N(εF)dG, which is consistent with the prediction of theAbrikosov–Gor'kov theory. We suggest that the depression of TCcould be mainly ascribed to the magnetic pair-breaking effect ofmagnetic Ho3+ ions. The change of Debye temperature with Ho contentmay not have significant impact on TC.