Lorentz microscopy of circular ferromagnetic permalloy nanodisks

Circular permalloy elements were fabricated by a combination of electron beam lithography, thermal evaporation and liftoff technique on electron transparent membrane substrates. The magnetic properties have been studied by Lorentz transmission electron microscopy. In situ magnetizing experiments have been carried out to obtain information about the nucleation and propagation of magnetic domains within the permalloy nanodisks and to determine the nucleation and saturation fields. The diameter of the patterned elements has been varied between 180 and 950 nm, the height was 15 nm. The experiments showed that the vortex configuration is the most favorable state in zero field conditions of all investigated permalloy nanodisks. (C) 2000 American Institute of Physics. [S0003-6951(00)05243-8].