Relativity shakes a magnet

March 03, 2014

The research group of Professor Jairo Sinova at the Institute of Physics at Johannes Gutenberg University Mainz (JGU), in collaboration with researchers from Prague, Cambridge, and Nottingham, have predicted and discovered a new physical phenomenon that allows to manipulate the state of a magnet by electric signals. Current technologies for writing, storing, and reading information are either charge-based or spin-based. Semiconductor flash or random access memories are prime examples among the large variety of charge-based devices. They utilize the possibility offered by semiconductors to easily electrically manipulate and detect their electronic charge states representing the "zeros" and "ones". The downside is that weak perturbations such as impurities, temperature change, or radiation can lead to uncontrolled charge redistributions and, as a consequence, to data loss. Spin-based devices operate on an entirely distinct principle. In some materials, like iron, electron spins generate magnetism and the position of the north and south pole of the magnet can be used to store the zeros and ones. This technology is behind memory applications ranging from kilobyte magnetic stripe cards to terabyte computer hard disks. Since they are based on spin, the devices are much more robust against charge perturbations. However, the drawback of current magnetic memories is that in order to reverse the north and south poles of the magnet, i.e., flip the zero to one or vice versa, the magnetic bit has to be coupled to an electro-magnet or to another permanent magnet. If instead one could flip the poles by an electric signal without involving another magnet, a new generation of memories can be envisaged combining the merits of both charge and spin-based devices.

In order the shake a magnet electrically without involving an electro-magnet or another permanent magnet one has to step out of the realm of classical physics and enter the relativistic quantum mechanics. Einstein's relativity allows electrons subject to electric current to order their spins so they become magnetic. The researchers took a permanent magnet GaMnAs and by applying an electric current inside the permanent magnet they created a new internal magnetic cloud, which was able to manipulate the surrounding permanent magnet. The work has been published in the journal Nature Nanotechnology on 2 March 2014.

The observed phenomenon is closely related to the relativistic intrinsic spin Hall effect which Jörg Wunderlich, Jairo Sinova, and Tomas Jungwirth discovered in 2004 following a prediction of Sinova and co-workers in 2003. Since then it has become a text-book demonstration of how electric currents can magnetize any material. "Ten years ago we predicted and discovered how electric currents can generate pure spin-currents through the intrinsic structure of materials. Now we have shown how this effect can be reversed to manipulate magnets by the current-induced polarization. These new phenomena are a major topic of research today since they can lead to new generation of memory devices. Besides our on-going collaborations, this research direction couples very well with on-going experimental research here in Mainz. Being part of this world-leading research and working with superb colleagues is an immense privilege and I am very excited about the future", says Professor Jairo Sinova.

Johannes Gutenberg Universitaet Mainz

Related Memories Articles from Brightsurf:

Can sleep protect us from forgetting old memories?
Researchers at University of California San Diego School of Medicine report that sleep may help people to learn continuously through their lifetime by encoding new memories and protecting old ones.

Why are memories attached to emotions so strong?
Multiple neurons in the brain must fire in synchrony to create persistent memories tied to intense emotions, new research from Columbia neuroscientists has found.

False memories of crime appear real when retold to others
People are no better than chance at identifying when someone else is recounting a false or real memory of a crime, according to a new UCL study published in Frontiers in Psychology.

Can traumatic memories be erased?
Tokyo, Japan - Scientists from Tokyo Metropolitan University have discovered that Drosophila flies lose long-term memory (LTM) of a traumatic event when kept in the dark, the first confirmation of environmental light playing a role in LTM maintenance.

The way of making memories
How does the brain translate information from the outside world into something we remember?

A new discovery: How our memories stabilize while we sleep
Scientists at the Center for Interdisciplinary Research in Biology (CNRS/Coll├Ęge de France/INSERM) have shown that delta waves emitted while we sleep are not generalized periods of silence during which the cortex rests, as has been described for decades in the scientific literature.

How memories form and fade
Caltech researchers identify the neural processes that make some memories fade rapidly while other memories persist over time.

Firework memories
Recently Weizmann Institute scientists succeeded in recording these rapid bursts of activity -- called 'hippocampal ripples' -- in the human brain, and they were able to demonstrate their importance as a neuronal mechanism underlying the engraving of new memories and their subsequent recall.

Your nose knows when it comes to stronger memories
Memories are stronger when the original experiences are accompanied by unpleasant odors, a team of researchers has found.

Proof it's possible to enhance or suppress memories
Boston University neuroscientist Steve Ramirez and collaborators have published a new paper showing memories are pliable if you know which regions of the brain's hippocampus to stimulate, which could someday enable personalized treatment for people with PTSD, depression and anxiety.

Read More: Memories News and Memories Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to