In magnetic random access memories (MRAMs), submicrometer-size magnetic structures store digital information in their magnetic orientation. In the most common architecture, the stored information can be retrieved by sensing the electrical resistance difference that exists in the magnetic structures between the two possible magnetization directions, using an effect called giant magnetoresistance. As long as the bit is not rewritten, the information is maintained; hence MRAM is a nonvolatile memory. The most appealing characteristics of MRAM are its miniaturization to deep submicrometer memory bits, its unlimited read-write capability, and its fast access. MRAM circuits are expected to be available in consumer products by 2003.