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January 12, 2012

IBMs new experimental atomic-scale magnet memory is at least 100 times denser than conventional memory

Scientists from IBM Research (NYSE: IBM) have successfully demonstrated the ability to store information in as few as 12 magnetic atoms. This is significantly less than today’s disk drives, which use about one million atoms to store a single bit of information. The ability to manipulate matter by its most basic components – atom by atom – could lead to the vital understanding necessary to build smaller, faster and more energy-efficient devices.

While silicon transistor technology has become cheaper, denser and more efficient, fundamental physical limitations suggest this path of conventional scaling is unsustainable. Alternative approaches are needed to continue the rapid pace of computing innovation.

By taking a novel approach and beginning at the smallest unit of data storage, the atom, scientists demonstrated magnetic storage that is at least 100 times denser than today’s hard disk drives and solid state memory chips. Future applications of nanostructures built one atom at a time, and that apply an unconventional form of magnetism called antiferromagnetism, could allow people and businesses to store 100 times more information in the same space.
Writing and reading a magnetic byte: this image shows a magnetic byte imaged 5 times in different magnetic states to store the ASCII code for each letter of the word THINK, a corporate mantra used by IBM since 1914. The team achieved this using 96 iron atoms − one bit was stored by 12 atoms and there are eight bits in each byte

Science - Bistability in Atomic-Scale Antiferromagnets




Control of magnetism on the atomic scale is becoming essential as data storage devices are miniaturized. We show that antiferromagnetic nanostructures, composed of just a few Fe atoms on a surface, exhibit two magnetic states, the Néel states, that are stable for hours at low temperature. For the smallest structures, we observed transitions between Néel states due to quantum tunneling of magnetization. We sensed the magnetic states of the designed structures using spin-polarized tunneling and switched between them electrically with nanosecond speed. Tailoring the properties of neighboring antiferromagnetic nanostructures enables a low-temperature demonstration of dense nonvolatile storage of information.

How it Works

The most basic piece of information that a computer understands is a bit. Much like a light that can be switched on or off, a bit can have only one of two values: "1" or "0". Until now, it was unknown how many atoms it would take to build a reliable magnetic memory bit.

With properties similar to those of magnets on a refrigerator, ferromagnets use a magnetic interaction between its constituent atoms that align all their spins – the origin of the atoms’ magnetism – in a single direction. Ferromagnets have worked well for magnetic data storage but a major obstacle for miniaturizing this down to atomic dimensions is the interaction of neighboring bits with each other. The magnetization of one magnetic bit can strongly affect that of its neighbor as a result of its magnetic field. Harnessing magnetic bits at the atomic scale to hold information or perform useful computing operations requires precise control of the interactions between the bits.

The scientists at IBM Research used a scanning tunneling microscope (STM) to atomically engineer a grouping of twelve antiferromagnetically coupled atoms that stored a bit of data for hours at low temperatures. Taking advantage of their inherent alternating magnetic spin directions, they demonstrated the ability to pack adjacent magnetic bits much closer together than was previously possible. This greatly increased the magnetic storage density without disrupting the state of neighboring bits.

14 pages of supplemental information

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