Apr 24 2007
A paper written by Northeastern University researchers has been named one of the Best Papers of 2006 by The Journal of Physics: Condensed Matter. The authors, Drs. Soack Dae Yoon, Carmine Vittoria, Vincent Harris, and their students had their paper detailing a new route to spintronics materials selected based upon the popularity of the paper with readers and the high praise it received from the magazine’s Board and a panel of judges. The U.K.-based journal reports on the experimental and theoretical studies of the structural, thermal, mechanical, electrical, magnetic, optical and surface properties of condensed matter.
Spintronics, short for spin electronics, is a new field of electronics that looks to harness not only the charge of an electron, as is done in conventional electronics, but its spin as well. Spintronic devices have similar diodes and transistors as conventional electronics, but potentially can be made smaller and use less power. Furthermore, the additional degree of freedom offered by electron spin allows greater functionality of these fundamental devices. Researchers believe that spintronics will eventually enable manufacturers to build a new class of smaller, cheaper, and better-performing devices that use less power.
While magnetic materials can posses a spin polarized current, semi-conductors, the building-blocks of electronics, have none. Consequently, scientists have been trying to add magnetic elements to semi-conductors to increase their magnetism and spin currents. While some researchers have achieved this, the problem has been that these materials only work at extremely low temperatures – not conducive to electronics, which must operate at room temperature even as they generate heat.
Harris, Vittoria and Yoon set about trying to create magnetic semi-conductors. To do this, they added manganese, a magnetic element, to TiO2, a semi-conducting material.
“Things began to get interesting when we noticed the data trending in an unexpected way,” says Harris. “We noticed that the TiO2 was becoming more magnetic the less manganese we added. When we omitted the manganese altogether we were shocked to see a robust magnetic signal.”
Further studies revealed that the source of the magnetic signal was from defects created in those TiO2 samples processed under low oxygen pressures. The lack of oxygen created Ti3+ cations which are magnetic.
Even more surprising, the defected TiO2 materials were magnetic at high temperatures – well above room temperature to 1100 degrees Fahrenheit – eliminating the previous problem of spintronics devices that only worked at very low temperatures.
Harris and colleagues submitted their paper on the topic to the Journal of Physics: Condensed Matter. After 3 months, the paper had been downloaded 250 times, after 6 months that number reached more than 500.
“The journal editors told us that less than 1% of their papers got this kind of attention,” says Harris.
Northeastern University researcher's are now working on a follow-up paper on the fundamentals of electronic transport in this new material, one that he believes may also generate a great deal of interest in the community.
"For decades the electronics community has labored to make materials as perfect as possible. This breakthrough surprised many since it essentially came about by making materials of poor quality, that is, loaded with defects," says Harris.