Structural, magnetic, and heat-capacity studies on Zn- and Ga-substituted PrBa₂Cu₃O_7-δ

Abstract

The compound PrBa₂Cu₃O_7-δ is not superconducting and exhibits antiferromagnetic ordering of the Pr moments with Neel temperature T_N of ~17 K. We have carried out magnetic, heat-capacity, and neutron-diffraction structural studies on Zn- and Ga-substituted PrBa₂Cu₃O_7-δ. The Zn and Ga dopants presumably substitute at the plane and the chain Cu sites, respectively. Our measurements reveal that T_N is reduced in both cases; the reduction being faster for Ga substitution than for Zn substitution. For 10 at. % Zn substitution T_N is ~15-16K, while for the same substitution level of Ga it is ~12-14 K. It is rather unusual that the plane-site substitution has relatively less effect on T_N than the chain-site substitution. From neutron-diffraction studies the cause of such contrasting behavior may be understood in terms of changed planar Cu-O₂ and Pr-O₂ bond lengths. The electronic specific-heat coefficient γ of the substituted samples is found to be large as in the parent PrBa₂Cu₃O_7-δ compound.