Magnetic information can be transferred across an insulating material separating two magnetic layers via electron spin, according to a research team at the National University of Singapore.
Despite the advent of solid state "hard drives" vast quantities of data are still held on magnetic disks on server farms around the world. However, magnetic data transfer can be sluggish and so new devices that operate in the terahertz frequency range are keenly sought, says Ariando. [Ariando et al., Nature Commun. (2016) 7, 11015, DOI: 10.1038/ncomms11015]
Magnetic interactions are usually mediated by short-range exchange or weak dipole fields. In addition, the range achieved would previously have required a metallic system to transmit the electrons across the magnetic layers. The NUS team, co-led by T Venkatesan hoped to extend this range. "With the recent advance in the technology for growing uniform magnetic layers just a few dozen atoms thick, the discovery by NUS team paves the way for the development of new spintronics devices," Ariando told Materials Today.
Team member Lü Weiming discovered that the use of a polar oxide insulator could increase the magnetic coupling range from approximately one nanometer to ten nanometers with the strength of the effect varying depending on the spacer thickness. The finding is quite surprising given that no electrons should be able to traverse this seemingly impenetrable layer unless the spacer were metallic, which would defeat the object of splicing in the spacer in the first place.
Visiting faculty member and co-author Michael Coey of Trinity College Dublin, Ireland, suggests that 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 neighboring atoms until the orbital motion reaches the other side," he explains. Spectroscopic measurements carried out by another member of the team, Surajit Saha, support the notion of this new magnetic phenomenon. The next step will be to see whether this effect can be exploited in a magneto optical device.
Venkatesan is hopeful that it won't take quite as long as did the discovery of anti-ferromagnetism by French physicist Louis Néel before it had its technological debut after sixty years. "I believe we will soon discover a use for the phenomenon in the terahertz frequency regime," he says. "It should not take 60 years to find an application for new discoveries in magnetism such as this."
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".