Fabrication of magnetic STM probes and their application to studies of the Fe3O4(0 0 1) surface

A reproducible technique for the fabrication of STM tips from a range of magnetic materials has been developed. The tips are formed by electrochemical etching in an aqueous solution (NaOH, HCl), using polymer tubing to physically restrict the active etching region. Tips have been produced from polycrystalline MnNi, Cr, Fe and Ni with apexes in the 50–100 nm range. Atomic resolution STM images have been achieved on the Fe3O4(0 0 1) surface, using MnNi tips, which are interpreted in terms of a possible spin-polarised effect.