PROPERTIES AND MEASUREMENT OF SCANNING TUNNELING MICROSCOPE FABRICATED FERROMAGNETIC PARTICLE ARRAYS (INVITED)

The low temperature magnetic properties of arrays of scanning tunnelin g microscope (STM) fabricated ferromagnetic particles have been studie d as a function of their dimension using a novel high sensitivity Hall magnetometer. Iron deposits with controlled shape and nanometer scale diameters (similar to 25 nm) are formed using a STM to decompose a me talorganic precursor [Fe(CO)(5)] in the active area of the measurement device. The hysteresis loops change significantly in going from nearl y isotropic to oriented high aspect ratio (6:1 length to diameter) fil amentary particles. In particles of intermediate aspect ratio and diam eter the largest coercive field of 2.7 kOe is observed. This behavior as well as the characteristics of the Hall magnetometer (spin sensitiv ity of 10(-14) emu/Hz(1/2)) are described.