R&D: Ecole Polytechnique Fédérale de Lausanne Introducing Light-Operated HDDs of Tomorrow

From EPFL (Ecole Polytechnique Fédérale de Lausanne), Lausanne, Switzerland

What do you get when you place a thin film of perovkite material used in solar cells on top of a magnetic substrate?

(scheme: © EPFL)

More efficient hard drive technology. László Forró, physicist, EPFL, and his team pave the way for the future of data storage.

“The key was to get the technology to work at room temperature,” explains László Forró, physicist, EPFL. “We had already known that it was possible to rewrite magnetic spin using light, but you’d have to cool the apparatus to  -180 degrees Celsius.”

Forró, along with his colleagues Bálint Náfrádi, and Endre Horváth, succeeded at tuning one ferromagnet at room temperature with visible light, a proof of concept that establishes the foundations of a new generation of hard drives that will be physically smaller, faster, and cheaper, requiring less energy compared to today’s commercial hard drives. The results are published in PNAS (see below).

A hard drive functions as a data storage device in a computer, where a large amount of data can be stored with an electromagnetically charged surface.

Nowadays, the demand for high capacity hard drives has increased more than ever. Computer users handle large files, databases, image or video files, using software, all of which require a large amount of memory in order to save and process the data as quickly as possible.

The EPFL scientists used a halide perovskite/oxide perovskite heterostructure in their new method for reversible, light-induced tuning of ferromagnetism at room temperature. Having a perovskite structure represents a novel class of light-absorbing materials.

(scheme: © EPFL)

As reported in the publication, “The rise of digitalization led to an exponential increase in demand for data storage. Mass-storage is resolved by hard-disk drives, HDDs, due to their relatively long lifespan and low price. HDDs use magnetic domains, which are rotated to store and retrieve information. However, an increase in capacity and speed is continuously demanded. We report a method to facilitate the writing of magnetic bits optically. 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. This is a viable alternative of the long-sought-after heat-assisted magnetic recording (HAMR) technology, which would heat up the disk material during the writing process.”

The method is still experimental, but it may be used to build the next generation of memory-storage systems, with higher capacities and with low energy demands. The method provides a stand for the development of a new generation of magneto-optical hard drives. Forró concludes: “ We are now looking for investors who would be interested in carrying on the patent application, and for industrial partners to implement this original idea and proof of principle into a product.”

Article: Tuning ferromagnetism at room temperature by visible light

PNAS (Proceedings of the National Academy of Sciences of the United States of America) has published an article written by Bálint Náfrádi, Péter Szirmai, Massimo Spina, Andrea Pisoni, Xavier Mettan, Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland, Norbert M. Nemes, GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain, and Unidad Asociada ICMM-CSIC ‘Laboratorio de Heteroestructuras con Aplicacion en Espintronica,’ Consejo Superior de Investigaciones Cientificas, 28049 Madrid, Spain, László Forró, and Endre Horváth, Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.

Significance: “The rise of digitalization led to an exponential increase in demand for data storage. Mass storage is resolved by hard disk drives (HDDs) due to their relatively long lifespan and low price. HDDs use magnetic domains, which are rotated to store and retrieve information. However, an increase in capacity and speed is continuously demanded. We report a method to facilitate the writing of magnetic bits optically. 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. This is a viable alternative to the long-sought-after heat-assisted magnetic recording (HAMR) technology, which would heat up the disk material during the writing process. “

Abstract: “Most digital information today is encoded in the magnetization of ferromagnetic domains. The demand for ever-increasing storage space fuels continuous research for energy-efficient manipulation of magnetism at smaller and smaller length scales. Writing a bit is usually achieved by rotating the magnetization of domains of the magnetic medium, which relies on effective magnetic fields. An alternative approach is to change the magnetic state directly by acting on the interaction between magnetic moments. Correlated oxides are ideal materials for this because the effects of a small external control parameter are amplified by the electronic correlations. Here, we present a radical method for reversible, light-induced tuning of ferromagnetism at room temperature using a halide perovskite/oxide perovskite heterostructure. We demonstrate that photoinduced charge carriers from the CH₃NH₃PbI₃ photovoltaic perovskite efficiently dope the thin La_0.7Sr_0.3Mn_O3 film and decrease the magnetization of the ferromagnetic state, allowing rapid rewriting of the magnetic bit. This manipulation could be accomplished at room temperature; hence this opens avenues for magnetooptical memory devices.“