Superparamagnetism and the future of magnetic random access memory

The role of superparamagnetism in determining the ultimate density of magnetic random access memory is investigated. Numerical calculations show that superparamagnetism can easily be stabilized even in elements of just a few nanometers in size by the shape anisotropy generated in elements with lateral elongation. The limitation to increasing density is shown to come not directly from superparamagnetism, but from, the high current densities which will be required to write data to elements that have been stabilized against superparamagnetism. Experimental measurements on planar elliptical Permalloy nanoelements show the capability of shape anisotropy to generate large stabilization fields. (C) 2003 American Institute of Physics.