Coming to a computer near you: Magnetic Memory

Magnets that remember could be the next big thing in computer memory In read mode, a small current passes through the tunneling barrier of the memory cell. The cell resistance is measured and compared with a reference cell to determine its state (0 or 1). In write mode, a current through the trace above the free magnetic layer generates a magnetic field. The direction of the current determines the type of magnetic moment established in the free magnetic layer. The alignment or nonalignment of the two magnetic layers determines if the cell stores a 0 or a 1. Recently, Motorola successfully demonstrated a 256-kbit magnetic RAM. The chip had a read/write cycle time of 35 nsec and consumed 24 mW at 3V. Motorola believes such chips may one day replace all existing semiconductor memories. Some day soon, we may have trouble explaining to our kids the concept of a computer booting up. Just as vacuum-tube radios and their obligatory warm-up time now seem quaint, so too will computers with a boot up delay. Magnetic solidstate memory could make it so. Besides promising instant-oncomputing, magnetic memorycould also hold the key to minimizing power consumption. With reduced power demands, it may wellbecome the memory of choice forthe growing number of power-hungry portable computing devices. Compared to ordinary volatile semiconductor memory, magneto-resistive random access memory (MRAM) seems too good to be true. MRAM combines the three most desirable memory attributes; speed, density, and nonvolatility. This triad is the Holy Grail of computer memory, and it may well help MRAM overtake all other types of memory. MRAM employs the magnetic tunneling junction principle. It stores data as magnetic moments rather than as electrical charge. A single memory cell consists of two magnetic layers separated by an insulating layer of aluminum oxide known as the tunneling