Synopsis: Two in one

A ferromagnetic semiconductor device combines memory and logic in a single architecture.
Synopsis figure
Credit: S. Mark et al., Phys. Rev. Lett. (2011)

One way to reduce power consumption in computers is to build memory and logical processing into a single structure, which avoids the heat generated by shuttling data (in the form of a current) back and forth.

In a paper appearing in Physical Review Letters, Stefan Mark and colleagues at the University of Würzburg, Germany, present a single device made out of the ferromagnetic semiconductor (Ga,Mn)As that combines read/write capability with a simple logical process.

The team carves 70-nm-thick (Ga,Mn)As into a miniature cross, with four narrow bars extending north, south, east, and west from a central, circular disk. Electrical current and magnetization are coupled in (Ga,Mn)As, so the magnetization of any one bar, which is always along its length, determines the spin polarization of a current running through it. The polarized current from a north-south or east-west bar magnetizes (writes) the central disk in either a “0” or “1” state, respectively. One reads the device by measuring the resistance across a tunnel junction connecting a bar and the disk. This resistance is higher for “1” than “0.” By merging two such devices, the team is also able to build simple “XOR” logical gates, and other logic gates are possible in principle.

(Ga,Mn)As is only ferromagnetic at low temperatures and not currently practical for applications. But when the right material comes along (and materials science is looking in this direction), Mark et al.’s device could be one of several promising all-electrical, nonvolatile alternatives to silicon. – Jessica Thomas


Announcements

More Announcements »

Subject Areas

Spintronics

Previous Synopsis

Atomic and Molecular Physics

Less wiggle room for the gravitational constant

Read More »

Next Synopsis

Nanophysics

Sharp end

Read More »

Related Articles

Viewpoint: Electrical Signal Picks Up a Magnet’s Heartbeat
Magnetism

Viewpoint: Electrical Signal Picks Up a Magnet’s Heartbeat

Excitations in a magnet coupled to a microwave cavity can be detected electrically, providing a new way to study magnets in the quantum regime. Read More »

Viewpoint: A Boost for Superconducting Logic
Superconductivity

Viewpoint: A Boost for Superconducting Logic

A new choice of materials leads to more practically useful superconducting spin valves. Read More »

Synopsis: Controlling Magnetism by Electricity
Magnetism

Synopsis: Controlling Magnetism by Electricity

Small voltages can control the magnetic properties of thin films at room temperature. Read More »

More Articles