A research group at the University of Tokyo has realized a magnet in which the north and south poles are inverted by passing a small current.
In recent years, research on technology for storing information as the direction of magnetization and reading it at high speed has been progressing.If new devices can be realized using such technology, it is expected that significant power reduction will be possible.
However, a large amount of power is generally required to change the direction of magnetization.Magnetization inversion is a method that transfers the direction of electron spin to magnetization, or a method that uses the force of spin orbit torque generated by passing an electric current through a two-layer structure in which a ferromagnetic metal thin film and a non-magnetic metal thin film are joined. However, in each case, a large current of about 2 Acm-107 is required.
This time, we made an ultra-thin film made of GaMnAs, a ferromagnetic semiconductor made by doping a semiconductor called gallium arsenide with a few percent of manganese atoms.By simply passing a current through this thin film, it is possible to reverse the magnetization with a very small current density of about 3.4 x 105 Acm-2.This value is about two orders of magnitude smaller than the current density required in conventional magnetization reversal research.
The group speculates that GaMnAs has properties as a magnet as well as a spin-activated interaction, which is a relativistic quantum effect, which enables magnetization reversal at low current densities. ..Furthermore, it was found that electrons (or holes) with large wave numbers need to contribute to conduction in order to fully utilize the spin-orbit interaction.From the above, it was found that if there is an electron with a large spin activation interaction and a large wave number inside the substance that becomes a magnet, it may be possible to reverse the magnetization with low power.
It is expected that this result will accelerate the search for new materials that can reverse the magnetization with low power.
Paper information:[Nature Communications] Efficient full spin-orbit torque switching in a single layer of a perpendicularly magnetized single-crystalline ferromagnet
