Magnetic memory cells meet the essential logical and economic requirements1,2of a memory cell and presently play a dominant role in electronically and mechanically accessed computer memories.3,4Electronically addressed magnetic memories typically are arranged in 3D, 2D, or 2½Dorganizations.5–9Progress in electronically addressed magnetic memories has resulted from a number of basic discoveries and developments in the threshold and switching properties of ferrite cores,10–12planar thin films,13–15and plated wires.16As recently summarized,17,18mechanically accessed memories such as tapes, drums, disks and data cells have had continual improvements in magnetic materials and in cell density. Present magnetic cells typically do not approach the limits set by thermal noise,19,9and, as a consequence, a substantial increase in density is possible. The number of magnetic memory cells produced each year is increasing by more than 30% per year3and continued growth can be anticipated.