Dis­rup­tive Paper May Pro­vide a New Alter­na­tive to Spin­tronics Mate­rials and Devices

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. Vin­cent Harris, Soack Dae Yoon, Carmine Vit­toria, Kate Ziemer and their col­leagues 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 and col­leagues 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.

For more infor­ma­tion, please con­tact Laura Shea at 617–373-5427 or l.​shea@​neu.​edu.

About North­eastern:

Founded in 1898, North­eastern Uni­ver­sity is a pri­vate research uni­ver­sity located in the heart of Boston. North­eastern is a leader in inter­dis­ci­pli­nary research, urban engage­ment, and the inte­gra­tion of class­room learning with real-​​world expe­ri­ence. The university’s dis­tinc­tive coop­er­a­tive edu­ca­tion pro­gram, where stu­dents alter­nate semes­ters of full-​​time study with semes­ters of paid work in fields rel­e­vant to their pro­fes­sional inter­ests and major, is one of the largest and most inno­v­a­tive in the world. The Uni­ver­sity offers a com­pre­hen­sive range of under­grad­uate and grad­uate pro­grams leading to degrees through the doc­torate in six under­grad­uate col­leges, eight grad­uate schools, and two part-​​time divi­sions. For more infor­ma­tion, please visit www​.north​eastern​.edu.