Making big strides in magnetoresistance research

Georgia State’s Dr. Ramesh Mani and his team made a discovery on Oct. 10,concerning the giant magnetoresistance effect in semiconductors that will significantly impact the way students use and view technology.

Mani and his team, through grants received from the U.S. Department of Energy and U.S. Army Research Office, found that the change of the resistance in a magnetic field relies on the size of the semiconductor devices.

The research will help those who work with or use semiconductors have a better understanding of its relationship with magnetoresistance. Magnetoresistance is now playing an integral role in modern technology. It is present in the anti-lock braking system in vehicles, helping detect when wheels are locking to avoid accidents.

Magnetoresistance can also help students store more files on the hard disk of their computers. By registering changes in electrical resistance on tiny, spinning magnets, where information is stored, Mani was able to find a more efficient way to retrieve and store information.

“It turns out that in our computers, the read-head in the hard disk uses a giant magnetoresistance effect to read out the information stored in small magnetic particles embedded in the platters of the hard disk.” Mani said.

Partly due to Mani’s advances in the read-head magnetoresistance, hard disk capacity has been rising year after year. Read-head sensors today can detect smaller magnetic fields than those a decade ago–and more information is being stored in less space.

“If you have used computers for several years, you may have noticed that the hard disk capacity has been increasing rapidly from year to year. One reason for this is that the technology for the magnetoresistance sensor in the hard disk read-head keeps improving with time. Since computers are a big part of the economy, one might say that magneto resistance technology is important,” Mani said.

He added that as long as researchers keep figuring out ways to pack smaller particles into the same area, hard disk capacity will continue to increase. Mani and his team studied magnetoresistance using a high-quality gallium arsenide semiconductor that contains flat thin sheets of electrons.

Mani highlighted the astonishing development of the hard disk from its beginnings of just being able to hold five million characters (3.75 megabytes) in 1956 a two-terabyte hard drive, where one terabyte is one million megabytes, according to TDK , a magnet manufacturing company.

“I think it is quite amazing,” Han-Chun Liu, a student of Mani, said.

“Wow, I had no idea that magnets had a lot to do with hard drives,” senior Justin Boyd said.

According to Mani, Georgia State’s physics undergraduate program enrollment has increased over the years, and he hopes that this research can possibly attract more students.

“If students learn about the intimate relation between magnetoresistance effects in various materials and the capacity of their hard disks, that will expand their knowledge base and show how things in this world can be interconnected. Perhaps, some students will find the effect fascinating and choose to study some more science or even physics. Of course, some physics majors may also decide that they want to study the effect in person,” Mani said.