Various technologies are under development in labs worldwide to dramatically enhance computer memory capacity beyond that of flash memory.
Magnetoresistive random access memory enables memory to be written and read in as little as a nanosecond thanks to its magnetization, but researchers are struggling to solve the problem of magnetization's tendency to spread to neighboring cells when changed. Meanwhile, ferroelectric random access memory (FeRAM) combines speed with low power demands, but its charge-based nature means that switching the ferroelectric with sufficient speed requires the additional charge to be stored in close proximity. Thus, every FeRAM memory cell has a capacitor attached to it, which takes up valuable space.
Phase-change random access memory (PCRAM) stores information in the atomic structure of materials with two distinct solid phases — an amorphous phase where the atoms are arranged in no specific pattern, and a patterned, crystalline phase. PCRAM offers extremely fast switching times but comes with high power requirements, although energy efficiency is likely to increase as the devices get smaller.
Resistive random access memory takes advantage of electrochemical reactions that change the bond structure of certain crystalline solids, creating stable memory states that can only be switched by the application of a high voltage of the correct polarity. "We can switch our devices in a nanosecond or less, and the energy required is in the order of a picojoule," says Hewlett-Packard researcher Stan Williams.
Racetrack memory is a concept, devised by IBM scientists, in which bits are stored as tiny domains of opposing magnetization that are threaded out along a nanoscale magnetic wire. Stuart Parkin of IBM's Almaden Research Center says that even a flat micrometer-sized wire could have storage capacity comparable to that of flash memory.
From New Scientist
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