Neutron Researchers Discover Widely Sought Property in Magnetic Semiconductor

Nov 25, 2008
Researchers working at NIST have confirmed that thin magnetic layers (red) of a semiconductor separated by a nonmagnetic layer (blue) can exhibit a coveted phenomenon known as "antiferromagnetic coupling," in which manganese (Mn) atoms in successive magnetic layers spontaneously orient their magnetization in opposite directions. This discovery, made by scattering neutrons (arrows) from the material, raises the prospects of "spintronic logic circuits" that could both store and process data. Credit: Brian Kirby, NIST

(PhysOrg.com) -- Researchers working at the National Institute of Standards and Technology have demonstrated for the first time the existence of a key magnetic—as opposed to electronic—property of specially built semiconductor devices. This discovery raises hopes for even smaller and faster gadgets that could result from magnetic data storage in a semiconductor material, which could then quickly process the data through built-in logic circuits controlled by electric fields.

Magnetic data storage is currently utilized with great success in consumer products such as computer hard drives and MP3 players. But these storage devices are based on metallic materials. These conventional hard drives can only hold data; they have to send the data to a semiconductor-based device to process the data, slowing down performance.

In a new paper, researchers from NIST, Korea University and the University of Notre Dame have confirmed theorists’ hopes that thin magnetic layers of semiconductor material could exhibit a prized property known as antiferromagnetic coupling—in which one layer spontaneously aligns its magnetic pole in the opposite direction as the next magnetic layer. The discovery of antiferromagnetic coupling in metals was the basis of the 2007 Nobel Prize in Physics, but it is only recently that it has become conceivable for semiconductor materials. Semiconductors with magnetic properties would not only be able to process data, but also store it.

The most widely studied magnetic semiconductor is gallium arsenide (GaAs) with magnetic atoms (manganese) taking the place of some of the gallium atoms. Theorists had predicted that by creating thin films of this material separated by a nonmagnetic material of just the right thickness and electrical properties, one could engineer antiferromagnetic (AF) coupling. With magnetic fields, one could then switch the magnetization of one of the layers back and forth to create “spintronic” logic circuits, ones that operate not only under the usual control of electric fields but also the influence of magnetic fields (manipulating a property known as spin, which could be imagined as tiny internal bar magnets in particles such as electrons).

The team, working at the NIST Center for Neutron Research, studied these multilayer stacks using a technique known as polarized neutron reflectometry. In this technique, a beam of neutrons is bounced off the stacks. Since neutrons are magnetic, and are able to easily penetrate through the entire stack, the reflected neutrons provide information about the magnetic properties of the individual layers. At low temperatures and small magnetic fields, the polarized neutron data unambiguously confirm the existence of an antiparallel magnetic alignment of neighboring layers. When the magnetic field was increased, the neutron data indicated a parallel alignment of all layers. These results demonstrate that AF coupling is achievable in GaMnAs-based multilayers, a seminal property that now opens up a multitude of device possibilities for this novel material. While the phenomenon only occurs at very cold temperatures in the material (about 30 K), the researchers believe these results will help inform theorists who could then better understand how to create room-temperature devices with the same magnetic properties.

Citation: J.-H. Chung, S.J. Chung, S. Lee, B.J. Kirby, J.A. Borchers, Y.J. Cho, X.Liu and J.K. Furdyna, Carrier-mediated antiferromagnetic interlayer exchange coupling in diluted magnetic semiconductor multilayers Ga1-xMnxAs/GaAs:Be. Physical Review Letters, to be published.

Source: National Institute of Standards and Technology

Explore further: Neutron tomography technique reveals phase fractions of crystalline materials in 3-dimensions

add to favorites email to friend print save as pdf

Related Stories

A new multi-bit 'spin' for MRAM storage

Jul 22, 2014

Interest in magnetic random access memory (MRAM) is escalating, thanks to demand for fast, low-cost, nonvolatile, low-consumption, secure memory devices. MRAM, which relies on manipulating the magnetization ...

Toward ultimate light efficiency on the cheap

Jul 16, 2014

(Phys.org) —Researchers at the University of Michigan have taken a major stride toward perfectly efficient lighting that is also relatively inexpensive and simple to make. The same material can also reveal ...

From pencil marks to quantum computers

Jul 03, 2014

Pick up a pencil. Make a mark on a piece of paper. Congratulations: you are doing cutting-edge condensed matter physics. You might even be making the first mark on the road to quantum computers, according ...

Recommended for you

50-foot-wide Muon g-2 electromagnet installed at Fermilab

13 hours ago

One year ago, the 50-foot-wide Muon g-2 electromagnet arrived at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Illinois after traveling 3,200 miles over land and sea from Long Island, ...

Spin-based electronics: New material successfully tested

Jul 30, 2014

Spintronics is an emerging field of electronics, where devices work by manipulating the spin of electrons rather than the current generated by their motion. This field can offer significant advantages to computer technology. ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

zevkirsh
1.5 / 5 (2) Nov 25, 2008
this , combined with AI and magneti
cally reprogrammable circuitry will help expedite the beginning of a new phase of a-i chips.
theophys
not rated yet Nov 28, 2008
Neato
This probably won't turn up any practical inventions for another decade or two, but neato none the less