Magnetic properties of superconductingK3C60and

Abstract

Single crystals of C&o were doped with alkali metal (K and Rb), characterized, and measured magnetically in fields up to 5 T. Detailed experiments show the samples to be of high quality with superconducting transition widths on the order of 1 K. Data on the field and temperature dependences of the critical current density J& and Hc& are presented. We find that while the general behavior is similar to that of powder specimens, there are significant differences when comparing magnitudes. We attribute these differences to the fact that powder samples have much more surface area per volume than single crystals which can affect the determination of superconducting parameters. The critical current density also shows clear differences when compared to polycrystalline samples. In addition, comparisons between K3C6o and Rb3C6o indicate that defects may be more prevalent in the latter compound due to more sensitive synthesis requirements.

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

“…[209], who measured the irreversible M (T ) curves. Additionally, in several publications small values of the penetration field were obtained [204,210,211], but attributed to the breaking of intergranular coupling. Moreover, in more direct measurements of λ [212,213] by µSR experiments the penetration depth was found to be 480 nm for K 3 C 60 and 420 nm for Rb 3 C 60 , which leads to µ 0 H c1 (0) = 4 · 0 and 4·9 mT respectively, while from optical reflectivity measurements [214] the penetration depth for K 3 C 60 and Rb 3 C 60 was found to be 800 nm.…”

“…The magnitude of λ obtained in this way is of the order of 200-250 nm (Table 2). [196] 30-38 2 · 14 [195] 480 [212] 3 · 4 [181, [195] 194] 19 · 7 [191] 38 [196] [192] 1 · 3 [181] 62 [192] 3 · 28 [192] 420 [213] 3 [194] 76 [196] 3 · 86 [196] [211] In these experiments the lower critical field was defined as the field at which a deviation from linearity in M (H ) first appeared. Indeed, an ideal superconductor exhibits linear M (H ) behaviour up to H c1 , where a sharp cusp occurs.…”

Mixed-state parameters and vortex pinning in single-crystallineK3C60fullerene superconductors

“…6,9,42,43 According to these results, the width of the hysteresis loops increases with sample size, although not proportionally. This can be explained by weaker pinning in single crystals compared to powder samples, due to the much smaller number of pinning centers in the more perfect structure of the crystals.…”

Unifying Chemical and Physical Principles for Oxide Superconductivity Based on an Anionic Charge Order Model

“…For this reason, self doping in complex cuprates (based on M"Bi, Hg, Tl) is here excluded although it can be similarly dealt with. However, a comparison is drawn with related cases such as doped fullerenes (e.g., Rb C ) (8). Common features with cuprates are a lattice of antibonding radicals.…”