Electronic properties of Sr14Cu24O41

Abstract

Crystals of orthorhombic Sr14Cu24O41 are semiconducting, with an activation energy of 0.18(2) eV for conduction along c, the direction lying parallel to both the (Cu2O3) planes and the (CuO2) chains. The magnetic susceptibility above 80 K follows a Curie-Weiss law with =-95 K and peff=0.65B/Cu in the ac plane and =-190 and peff=0.94B/Cu along b, the direction perpendicular to the (Cu2O3) planes and the (CuO2) chains. There is an indication of antiferromagnetic order below TN=60 K, and a Curie contribution at low temperature due to localized free spins [0.4(1) with S=(1/2 per formula]. The specific heat measured in the range 212 K is of the form AT-2+T+T3, where A=1080 mJ K/mole, =100 mJ/mole K2, and =5.93 mJ/mole K3. A 5-T magnetic field greatly enhances the low-temperature specific heat, an effect which is attributed to the localized states with S=(1/2. The linear term is attributed to a localized density of states with no net spin, possibly associated with peroxide ions. The relevance of these results to the low-temperature specific heat of copper-oxide superconductors is discussed.