In materials science, magnetic and electrical effects have been observed separately for a long time: Magnetic material properties are usually influenced by magnetic fields, electrical properties by voltage. However, a special class of materials, the so-called multiferroika, combine both. Now, researchers at the Vienna University of Technology have succeeded in controlling magnetic oscillations of certain ferrous materials by means of electric fields. This opens up promising possibilities for computer technology, where data is transmitted in the form of electrical signals but stored magnetically.
Solid state physics often involves material properties that can be influenced by magnetic or electrical fields. However, magnetic and electrical effects can usually be considered separately because they have different causes: Magnetic effects come from the fact that particles have an inner magnetic direction, the so-called spin. Electrical effects, on the other hand, have to do with the fact that there are positive and negative charges in the material, which can shift spatially to each other.
“In materials with very specific spatial symmetries, both can be combined,” says professor Andrei Pimenov from the Institute of Solid State Physics at the Vienna University of Technology. Multiferroika are regarded worldwide as a promising new field in solid state physics. Pimenov and his team succeeded for the first time in controlling high-frequency magnetic oscillations of a material made of iron, boron and rare earth with electric fields.
“The material contains triple positively charged iron atoms. They have a magnetic moment that oscillates at a frequency of 300 GHz,” says Pimenov. “While it would be obvious to control such vibrations with a magnetic field, we have been able to demonstrate that these vibrations can be selectively varied by means of an electrical field.” A dynamic magnetic effect – a magnetic oscillation state of the iron atoms – can therefore be switched on or off by a static electric field.
This effect could be relevant for future electronics: “Hard disks store data magnetically. However, it is quite difficult to write data magnetically fast and precisely,” says Pimenov. “It’s much easier to apply an electric field with extreme accuracy, and a simple voltage pulse is all that’s needed to do so, which is very fast and without any significant energy losses.” Materials that combine magnetic and electrical effects could potentially combine the benefits of magnetic storage and electrical writing.
Original publication: Switching of Magnons by Electric and Magnetic Fields in Multiferroic Borates, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.027203