Switching of nanoscale magnetic elements

We have investigated the magnetic properties of ultra-small-patterned elements of Co and NiFe thin films. The elements were rectangular with an aspect ratio in the range 3.75-20. The smallest were 200 x 40 nm(2) with 50 nm gaps between them, corresponding to an areal density of 27 Gbit/in(2) if used as discrete-patterned media for magnetic recording. The elements were fabricated by electron-beam lithography and lift-off patterning and high-resolution magnetic images were obtained by Lorentz microscopy in a transmission electron microscope. In situ magnetization reversal experiments showed that the strong dependence of the switching field on element width extended to the smallest elements of both materials. The switching field for 40-nm-wide Co elements was 1200 Oe and for 40-nm-wide NiFe elements was 800 Oe. Element length and aspect ratio had little effect. (C) 1999 American Institute of Physics. [S0003-6951(99)02749-7].