Turn the light on and off with spin

Canadian and US researchers have released information about a new material that can turn off or open the light beam by changing the spin polarization of electrons in the material. This material is made from small magnetic Cobalt particles covered partially by Gold (Au). According to the researchers, there will be a day the material can be used in components to process information to enable both light and electron spin.

Dr. Abdul Y. Elezzabi (University of Alberta, Edmonton, Alberta T6G 2V4 Canada)

Currently, many studies are focused on developing spintronic devices that use the spin properties of electrons simultaneously to store and process information. Simultaneously with these studies, there are many other studies that seek to exploit the interaction between light and the collective vibrations of electrons at the metal surface (surface plasmon effect), to create components. plasmon for information processing and transmission.

Recently, Abdul Elezabbi and Kenneth Chau of the University of Alberta (Canada) with Mark Johnson (Naval Research Laboratory in Washington DC, USA) have created a combination of spintronics and plasmon materials to open and close. a light beam with THz frequency. When the material is applied to an external magnetic field, the electrons in the Co particles (micron-sized) are subject to spin polarization. When light in the THz frequency range shines on the material, the electromagnetic field of light drives the spin-polarized electrons from Co to the covered gold (see figure). This results in a change in resistance between gold and Co, and is called anisotropic Magneto Resistor (AMR).

When the magnetic field is turned off, the AMR effect disappears and much of the light passes through the material through the plasmon effect. However, when the magnetic field is reset, the increase in resistance due to the AMR effect interferes with the plasmonic flow and light passes through the material to more than 70% in many samples.

(Photo: Vatlyvietnam)

Elezabbi told Physics Web that the team observed this collapsible effect in many other magnetic materials and is currently trying to find other materials to enhance this effect. Elezabbi said that on the principle that this effect is not limited to light in the THz band - located between the microwave and ultraviolet bands - but it is difficult for higher frequencies because the electric field of the light will oscillate. so fast that electronic polarized spin could not move to the gold covered area.

Elezabbi also added that the group is currently in the process of completing a patent related to some components that apply this effect. The results have just been published in Physical Review Letters .

Physics - Vietnamese Physics (According to Hamish Johnston - PhysicsWeb.org)