Magnetic memory

Magnetic memory is as old as digital electronics. It has the incontrovertible advantages of being nonvolatile and indefinitely rewritable. Mass memory for computers has been provided by hard discs for over 50 years. A series of ideas have been advanced for other, faster, schemes which can be addressed electrically, rather than mechanically. These included ferrite core memory which was dominant in the 1950s and 1960s, until it was superseded by semiconductor memory, permalloy plated wire memory in the 1960s, magnetic bubble memory in the 1970s and early 1980s, and magnetic random-access memory (MRAM) which has been under development since the mid 1990s. In principle, MRAM can combine the speed of SRAM with the density of DRAM and the nonvolatility of flash, with radiation hardness and reduced power consumption. The latter has always been an attraction of magnetic memory for military and space applications – the computers in the Challenger space shuttle and the Hubble Space Telescope include magnetic memory. With increasing miniaturization radiation hardness could become an issue for civilian applications because of the problems associated with unshieldable background radiation.