Physicists at the École polytechnique fédérale de Lausanne (EPFL) in Switzerland have altered a magnetic bit’s polarity with light, potentially opening the way to denser and faster disk drives using magneto-optical technology.
Researchers László Forró, Bálint Náfrádi and Endre Horváth suggest magneto-optical drives using this method could be physically smaller, faster and cheaper than today’s disk drives. They also say it is an alternative to heat-assisted magnetic recording (HAMR).
They are now seeking investors to back a patent application and industrial partners to productise the proof of concept demonstration.
The EPFL team used visible light waves to write and re-write magnetic bits at room temperature. Previously it had only been possible by cooling a magnet to –180 degrees Celsius.
The researchers used a halide perovskite/oxide perovskite heterostructure, and the abstract of their scientific paper states “demonstrate that photo-induced charge carriers from the CH3NH3PbI3 photovoltaic perovskite efficiently dope the thin La0.7SR0.3MnO3 film and decrease the magnetization of the ferromagnetic state, allowing rapid rewriting of the magnetic bit.”
A photovoltaic substance converts light into electricity. The word ‘perovskite” refers to a calcium titanium oxide mineral (CaTiO3) and the term is also used for a class of compounds which have the same type of crystal structure. Perovskites are used in solar cells.
In a heterostructure the chemical composition of the structure changes as the position within the structure changes. For example, and simplistically, a semiconductor could have dissimilar crystalline regions either side of the interface between them.
The Swiss researchers placed a thin film of perovskite material on top of a magnetic substrate. Their paper states: “We use a sandwich of a highly light sensitive (MAPbI3) and a ferromagnetic material (LSMO), where illumination of MAPbI3 drives charge carriers into LSMO and decreases its magnetism.”
MAPbI3 is Methylammonium lead bromide and LSMO is Lanthanum strontium manganite; both are perovskites.
The EPFL full paper is published behind a paywall by PNAS (Proceedings of the National Academy of Sciences of the USA).