Hybridization, hole localization and pair breaking in the high Tc superconducting system Y1-xPrxBa2Cu3O7-δ

MAPLE, M.B.; LEE, B.W.; NEUMEIER, J.J.; NIEVA, G.; PAULIUS, L.M.; SEAMAN, C.L.

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Año: 1992 vol. 181 p. 135 - 152

0925-8388

The Y1-xPrxBa2Cu3O7-δ (δ ≈ 0.05) system has a rich temperature-praseodymium concentration (T-x) phase diagram consisting of a metal-insulator transition at xcr≈0.6, high Tc superconductivity in the metallic phase (0≤x≤xcr), and antiferromagnetic ordering of the Cu2+ and praseodymium ions at Néel temperatures TN(Cu) > TN(Cu)>TN(Pr) in the insulating phase (xcr≤x≤1). In the metallic phase, Tc decreases monotonically with x and vanishes near xcr, the dependence of Tc on pressure P and the upper critical field on temperature are both anomalous, and the low temperature specific heat can be resolved into a large γΓ contribution, reminiscent of heavy fermion behavior, and a spin 1 2 Kondo anomaly; in the insulating phase, the values of TN(Pr) are anomalously large. These phenomena are briefly reviewed within the framework of a picture that is based on appreciable hybridization of the praseodymium localized 4f states and the CuO2 valence band states. A phenomenological model that incorporates the annihilation of mobile holes in the CuO2 planes and superconducting electron pair breaking by the praseodymium ions can describe Tc (x,P) for x ≤ 0.2. © 1992.