Origin ofTcsuppression due toR=Eu, Nd, and Pr in superconducting (La1

Abstract

The origin of T c suppression due to substitution of rare-earth elements (R) is investigated for the samples of ͑La 1Ϫx R x ͒ 1.82 Sr 0.18 CuO 4 , ͑RϭEu,Nd,Pr͒ through the measurements of electrical resistivity and lattice parameters. With increasing x, three phases, T, T*, and TЈ appear successively and the critical concentration for disappearance of superconductivity exists in the T-phase region, each of which is xϭ0.12, 0.4, and 0.6 for RϭEu, Nd, and Pr, respectively, indicating that the smaller the ionic radius of the substituted R element, the stronger the T c suppression. Temperature dependence of the conductivity is described by ϰlnT above xϭ0.08 and 0.1 for RϭEu and Nd, respectively, but not for RϭPr. The origin of T c suppression is discussed in terms of two contributions; the reduction of the Madelung site potential at apical oxygen sites and the random potential scattering on the CuO 2 planes which is effective for pair breaking in d-wave superconductors, both of which are caused by displacement of apical oxygens due to substitution of R elements.

Normal-state anomalies in the transport and magnetic properties in the(La1−xPrxMusa1, Garcia2, Amaral3 et al. 1999Phys. Rev. B5000View full textAdd to dashboardCite

“…Pr was just chosen as the doping element because it is an out-ofplane substitution for which there is no evidence for tetra-or mixed valence or for hybridization with the electronic states of the conduction planes in LSCO, 12 leaving unchanged the hole concentration 13 and the oxygen content. 14 The effective magnetic moment of 3.52 B obtained for the Pr ions from our (x,T) measurements confirms its 3ϩ state. So, there is no need for the search of other than steric reasons as the source of the observed transport and magnetic properties.…”

“…As known, short-range dynamic antiferromagnetic ͑AF͒ correlations survive in the layered cuprates in the metallic compositions and even in the superconducting state, 15,16 with a correlation length that shortens with the increase in the concentration and mobility of the holes. 17,18 Since in the Pr:LSCO system the hole concentration remains constant even for large doping rates, 14 the systematic increase of the resistivity with x evidences a reduction in hole mobility, which would lead to an enhancement of the AF correlations. In principle, the emergence of broad maxima on cooling would be the expected signature of such enhancement in the (x,T) curves.…”

Magnetic-field-drivenx≈1/8anomaly of superconductivity inLa2−x−yLaiho1, Salminen2, Захвалинский3 2004Phys. Rev. B3030View full textAdd to dashboardCite

“…17,18 Local changes of the surroundings is very likely when a Mn 3ϩ ion with smaller radius replaces La 3ϩ in the lattice. 19 As shown in Fig. 3͑a͒ the values of T c (y) obtained from M (T) and S (T) agree quite well.…”