Ordering nanometer-scale magnets using bacterial thread templates

Nanometer-scale ferromagnetic particles (Fe2O3, Fe3O4) are dispersed within a mutant bacterial chain which is drawn into a macroscopic fiber "rope." Cross-sectional scanning electron microscopy images reveal that the iron oxide particles are intercalated between the walls of the bacterial cells which are bundled into parallel threads. The held-dependent switching is seen to markedly sharpen when the synthesis is conducted within an applied magnetic field. (C) 1998 American Institute of Physics.