Angle-dependence of the Hall effect in Hg-Ba-Ca-Cu-O thin films

Superconducting compounds of the family Hg-Ba-Ca-Cu-O have evoked intensive research efforts since the current record-holder for the highest critical temperature of a superconductor belongs to this class of materials. Thin films of the compound with two adjacent copper-oxide layers and a critical temperature of about 120 K were prepared by a two-step process that starts with the pulsed-laser deposition of precursor films and subsequent annealing in mercury-vapour atmosphere. Hg-Ba-Ca-Cu-O is a quasi-two dimensional material with high anisotropy, and, like some other high-temperature superconductors, exhibits a specific anomaly of the Hall effect, a double-sign change of the Hall coefficient close to the super-conducting transition. We have investigated this phenomenon by measurements of the Hall effect at different angles between the magnetic field direction and the crystallographic c axis. The results are discussed in terms of various contributions to the Hall effect by normal-state carriers, superconducting fluctuations, and dissipative vortex motion. (author)