Physical properties of a new cuprate superconductor Pr2Ba4Cu7O15-δ

• Published in: Science and technology of advanced materials Vol. 8; no. 6; pp. 477 - 483
• Main Authors: Matsushita, Akiyuki, Fukuda, Kazunori, Yamada, Yuh, Ishikawa, Fumihiro, Sekiya, Syun, Hedo, Masato, Naka, Takashi
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 01-09-2007; IOP Publishing; Taylor & Francis Group
• Subjects: High-T; Magnetic susceptibility; Pr-based cuprate; Specific heat; superconductor
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1016/j.stam.2007.07.003

We present studies of the thermal, magnetic, and electrical transport properties of reduced polycrystalline Pr
2
Ba
4
Cu
7
O
15−δ
(Pr247) showing a superconducting transition at T
c
=10-16 K, and compare them with those of as-sintered non-superconducting Pr247. The electrical resistivity in the normal state exhibited T
2
dependence up to approximately 150 K. A clear specific heat anomaly was observed at T
c
for Pr247 reduced in a vacuum for 24 h, proving the bulk nature of the superconducting state. By the reduction treatment, the magnetic ordering temperature T
n
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 3.13μ
B
. The sign of Hall coefficient changed from positive to negative with decreasing temperature in the normal state of a superconducting Pr247, while that of the as-sintered one was positive down to 5 K. The electrical resistivity under high magnetic fields was found to exhibit T
α
dependence (α=0.08-0.4) at low temperatures. A possibility of superconductivity in the so-called CuO double chains is discussed.
PACS: 74.72.Jt; 74.25.Bt; 75.40.Cx; 74.25.Fy