Magnetic force microscopy investigation of superconductors: first results

Abstract

We have performed our first magnetic force microscope (MFM) measurements on the high- T c superconductor Bi 2Sr 2CaCu 2O x and conventional type-1 superconductor Sn, with a specially designed low-temperature MFM. The magnetic interaction between ferromagnetic tip and Sn sample was detected and recorded as a function of the tip-sample distance. It is shown that the low-temperature MFM may be used to investigate the distribution of the superconductive phase on the surface of the superconductors. All MFM images of Bi 2Sr 2CaCu 2O x at T< T c show some perturbations and smooth regions, which may be treated as the regions with the disturbance of the superconductivity of the sample. The possible physical reason for the existence of such regions could be imperfections in the sample structure or more complex phenomena of the magnetic field penetration into the high- T c superconductor, which is caused by the tip.