Data storage: Magnetic memories
Magnetic random-access memory based on new spin transfer technology achieves higher storage density by packing multiple bits of data into each memory cell.
Solid-state memory is seeing an increase in demand due to the emergence of portable devices such as tablet computers and smart phones. Spin-transfer torque magnetoresistive random-access memory (STT-MRAM) is a new type of solid-state memory that uses electrical currents to read and write data that are stored on magnetic moment of electrons. Rachid Sbiaa and co-workers at the A*STAR Data Storage Institute1 have now enhanced the storage density of STT-MRAM by packing multiple bits of information into each of its memory cells.
"As a technology, STT-MRAM has several advantages," says Sbiaa. "They have high read and write speed, low power consumption, great endurance, and are easy to integrate with standard semiconductor-processing technologies." Further increasing the storage density remains a challenge, however, because the write current needs to be increased to keep the bit thermally stable. A solution to overcome this problem is to use memory cells that can hold multiple bits, but scientists have yet to achieve the electrical control needed for this kind of STT-MRAM.
Essentially, STT-MRAM reads and writes information by passing currents through multiple magnetic thin films. Information is written if the magnetic moment of electrons in the current, or spin, is aligned in one preferable direction. The torque by these aligned spins on the magnetic layers can be strong enough to switch the magnetic direction of the layers to the direction set by the current.
Reading information is done through the measurement of electrical resistance of the device, which depends on whether the magnetizations of the soft and hard magnetic layers are aligned in parallel or opposite directions relative to each other. The hard magnetic layer is designed in such a way that its magnetism cannot be switched by electric currents.
To store two bits, the researchers have now added a second soft magnetic layer. These two soft magnets are slightly different, one being ‘harder’ than the other, and can therefore be switched independently by a suitable choice of electrical current. In this way four possible combinations for the magnetic states can be addressed by electrical currents, corresponding to two bits of information (see image).
Furthermore, the researchers introduced magnetic layers polarized in the in-plane direction that enhance the torque effect and thereby reduce the overall electrical current required to write information.
In the future, the researchers plan to use a different device design based on electrons ‘tunnelling’ across an insulating layer. "These magnetic tunnel junctions provide a higher read signal than for a giant magnetoresistance-type device," says Sbiaa.
Enhanced magnetic storage devices. An electrical current passing through a stack of magnetic layers (left) is used to write and read magnetic information. The relative orientation of the soft magnetic layers encodes up to four bits (right).
The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute
Lee Swee Heng | Research asia research news
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...