The property of spin – the intrinsic angular momentum of the electrons – is hardly considered in semiconductor technology, apart from computer hard drives.

The electrical charge is primarily used to transmit, temporarily store and process information.

However, it has been shown that faster circuits and denser storage media are possible if spin instead of charge were used as the information carrier.

A field of research has meanwhile been established under the name of spintronics, which, in addition to the charge, also wants to utilize the "twist" of the electrons for rapid data processing.

Manfred Lindinger

Editor in the department "Nature and Science".

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Due to their intrinsic angular momentum and the associated magnetic moments, electrons behave like tiny bar magnets that can rotate quickly around their own axis.

Depending on the orientation, the spin of electrons can be used as a binary information carrier with the values ​​"0" and "1".

Processing information with spins would have many advantages.

The electron spin can be influenced and controlled more easily by magnetic fields than is possible with electric fields in the case of charges.

The information stored in the spins also reacts much less strongly to external disturbances, such as stray fields.

Data could also be processed much faster.

With spins as information carriers, there is also less heat loss because no electrons flow that collide with atoms of the conductor.

Voltage pulses that can be further processed electronically

Spintronics has found its first application in the read/write heads of modern computer hard drives.

These magnetic field sensors use an effect that the German solid state physicist Peter Grünberg discovered in 1988 at the Jülich Research Center.

He discovered that the electrical conductivity of thin ferromagnetic layers changes as soon as they are exposed to an external magnetic field.

In a read head, which is guided closely over a hard disk, the magnetic "ones" or "zeros" stored by spin are converted into voltage pulses that can be further processed electronically.

Another application of spintronics are magnetic working memories, so-called MRAMs.

These can store and release information faster than the conventional read-write memory of a microprocessor.

MRAMs don't lose their data when the power supply fails.

In addition, they are economical in terms of energy consumption and can be written to as often as required.

The smallest memory cell of a modern MRAM typically consists of two stacked thin ferromagnetic layers separated by an insulator.

An electric current with polarized electrons sent through the cell changes the magnetization of the two ferromagnets relative to each other.

This results in two distinguishable binary states of the memory cell - "1" or "0".

The current value of a bit can be read and further processed via the corresponding resistance value.

Due to the high price, MRAMs are primarily used in aerospace and industrial computer systems to prevent data loss in the event of a power failure.

Spin waves can superimpose on each other

If you want to transmit and process data with electron spins, you usually do not use individual spins as information carriers as in classical spintronics, but so-called spin waves, also known as magnons.

Like water or light waves, spin waves can propagate and overlap one another.

Here, the electrons themselves do not move through a ferromagnetic material, but are fixed in place.