Part of the team members from NUS Nanoscience and Nanotechnology Institute are: (from left to right) Dr. Renshaw Wang, Dr. Huang Zhen, Assistant Professor Ariando and Professor T. Venkatesan. They are looking at a four-inch wafer on which a multi-component oxide film has been deposited using the pulsed laser deposition process.
A team led by researchers from the National University of Singapore (NUS) has achieved a major breakthrough in magnetic interaction. By adding a special insulator, they make electrons “twirl” their neighbouring “dance partners” to transfer magnetic information over a longer range between two thin layers of magnetic materials. This new technique enables magnetic information to make their way from one magnetic layer to another, synonymous to encoding and transmission of data.
“The big data revolution relies on vast amount of digital information which are magnetically stored on hard disks in server farms across the planet. A bottleneck that stifles the progress of this emerging field lies in the demand for faster data transmission rates. The recent discovery by our team paves the way for the development of devices that operate in the terahertz frequency range, which makes encoding and transmission of data many times faster,” explained Assistant Professor Ariando, NUS.
While many people are used to downloading data from the Cloud onto mobile devices, most do not know where the data comes from. Digital information is stored in minute magnetic dots written in layers a few nanometers thick that cover the surface of millions of saucer-sized spinning disks. These hard disks are stacked by the thousands in server farms worldwide.
In recent years, the technology for growing uniform magnetic layers only 10 to 100 atoms thick has been perfected. By combining them into complex stacks, these nanostructures form the foundation of ‘spin electronics’. The spin makes the electron into a tiny magnet.
When two magnetic layers are stacked close to each other, they couple together to exchange electrons with each other. The electrons carry across their spin, and the directions of magnetisation of the two layers are aligned. This coupling is broken if the magnetic layers are separated by an insulating spacer more than a few atoms thick. The insulator is almost impenetrable for the free electrons. As magnetic interactions are normally mediated by short-range exchange or weak dipole fields, the research team, sought to propagate the magnetic interaction over longer distances.
Dr Lü Weiming found the use of polar oxide insulator enables the range of the magnetic coupling to jump from 1nm to 10, and its strength varies up and down with spacer thickness. This discovery is startling as no electrons could ever make their way across such an impenetrable layer. In addition, the range achieved would previously have required a metallic system to transmit the electrons across the magnetic layers.
To explain this unusual observation, Professor Michael Coey said. “Instead of spin magnetism being carried across directly by messenger electrons, it is the orbital magnetism that is passed along from atom to the next across the insulator. The atomic electrons are engaged in a dance, each twirling their partners on the neighbouring atoms until the orbital motion reaches the other side,” he explained. This was proven via spectroscopic measurements on the new magnetic effect.
They intend to further investigate the effect to fully understand the mechanism, and to utilise their discovery to develop a new generation of magneto optical devices.
http://news.nus.edu.sg/press-releases/10242-novel-transferring-magnetic-information
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