Transition metal (TM) fluoride electron beam sensitive resists suitable for the in situ fabrication of arbitrarily shaped nanometer scale magnetic structures have been developed. 20 nm thick TM fluoride films are prepared by thermal evaporation onto thin carbon films. Nanopatterns are written directly into the TM fluoride film in a scanning transmission electron microscope using a 0.5 nm diameter,electron probe. Electron energy loss spectroscopy measurements indicate that as fluorine is released, the TM coalesces. Electron micrographs of exposed patterns show that the resist resolution is on the order of nanometers. Exposure of broad areas leads to coalescent TM layers which cap the remaining fluoride and decrease the rate of fluorine removal. The cross section for the removal of a fluorine atom and the cross section for the same process in the presence of an arbitrarily thick capping layer were measured. An electron dose of 1000 C/cm(2) at 100 keV will remove 90% of the fluorine from a 20 nn thick CoF2 film.