Physical properties of a new cuprate superconductor Pr_2Ba_4Cu_7O_{15-\delta}

TL;DR

This study investigates the thermal, magnetic, and electrical properties of a new cuprate superconductor Pr_2Ba_4Cu_7O_{15-eta}, revealing bulk superconductivity at 10-16 K and discussing its unique transport behaviors and magnetic properties.

Contribution

It provides the first detailed analysis of the bulk superconducting properties and transport phenomena of Pr_2Ba_4Cu_7O_{15-eta}, highlighting the role of CuO double chains.

Findings

Superconducting transition at 10-16 K confirmed by specific heat anomaly.

Electrical resistivity shows T^2 dependence up to 150 K in the normal state.

Hall coefficient sign changes from positive to negative with decreasing temperature.

Abstract

We present studies of the thermal, magnetic and electrical transport properties of reduced polycrystalline Pr_2Ba_4Cu_7O_{15-\delta} (Pr247) showing a superconducting transition at Tc = 10 - 16 K and compare them with those of as-sintered non-superconducting Pr247. The electrical resistivity in the normal state exhibited T2 dependence up to approximately 150 K. A clear specific heat anomaly was observed at Tc for Pr247 reduced in a vacuum for 24 hrs, proving the bulk nature of the superconducting state. By the reduction treatment, the magnetic ordering temperature TN of Pr moments decreased from 16 to 11 K, and the entropy associated with the ordering increased, while the effective paramagnetic moments obtained from the DC magnetic susceptibility varied from 2.72 to 3.13 mB. The sign of Hall coefficient changed from positive to negative with decreasing temperature in the normal state of a superconducting Pr247, while that of as-sintered one was positive down to 5 K. The electrical resistivity under high magnetic fields was found to exhibit T^a dependence (a = 0.08 - 0.4) at low temperatures. A possibility of superconductivity in the so-called CuO double chains is discussed.