HIGH-SENSITIVITY MAGNETIZATION MEASUREMENTS OF NANOSCALE COBALT CLUSTERS

Presented is a novel high sensitivity magnetometer allowing us to meas ure the magnetization reversal of about 10(4) mu(beta) corresponding t o a sensitivity of about 10(-16) emu. The detector is a niobium micro- bridge DC superconducting quantum interference device (SQUID), fabrica ted using electron-beam lithography. It is operational in the temperat ure range of 0-7 K. Furthermore, we present a method to deposit on the SQUID loop a small number of Co clusters of about 2-5 nm in diameter. The first results obtained on these samples show that there is still a ferromagnetic coupling between the clusters and the magnetization re versal takes place by small avalanches. (C) 1995 American Institute of Physics.