Notre Dame eyes magnetic logic

February 16, 2006 – Researchers at the U. of Notre Dame have developed a prototype demonstrating a chip design approach that utilizes tiny magnets for logic functions instead of electrical transistors.

The device uses the same basic principle as quantum-dot cellular automata (QCA), by which quantum dots are arranged into cells lined up to form “binary wires” to form switches and various logic devices — a 1 sq. cm QCA chip would contain up to 1 trillion devices, vs. 6 million in today’s leading-edge chips. However, faced with limitations such as stray charges from the quantum dots and extremely low-temperature fabrication requirements, the researchers turned to nanomagnetic interactions, which already are used in memory and data storage. They claim to have fabricated a chip with a universal logic gate (NAND + NOR), that uses tiny “islands” of ~110nm-wide nanomagnets to manage binary codes as logic functions.

The magnets were created by evaporating a thin layer of ferromagnetic nickel/iron alloy onto a silicon surface, then patterning the “islands” using electron-beam lithography. A pulsed magnetic field on the input magnet alters the orientation of its magnetic field, resulting in a magnetostatic attraction and repulsion that causes fields of adjacent magnets to “flip.” A scanning probe was used to infer the magnetization.

With no transistor wires, density and power could be much higher, power consumption would be reduced, and the nonvolatile properties would mean data would be retained when the device is switched off.


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