Skip to main content

Ultrafast All-Optical Magnetization Reversal for Magnetic Recording and Laser-Controlled Spintronics

Final Report Summary - ULTRAMAGNETRON (Ultrafast all-optical magnetization reversal for magnetic recording and laser-controlled spintronics)

During the last decades the operation speed of computers has grown exponentially, while chip dimensions decreased, bringing the clock speed into the GHz range. However, the speed of magnetic storage of data and processing magnetically stored information, as on a hard disc or in Magnetic random access memory (MRAM), is presently limited to a few nanoseconds. Moreover, based on current technology of magnetization reversal the operation speed of these spintronic devices is approaching its practical limit. Consequently, the demand for the ever-increasing speed of information storage and manipulation has triggered an intense search for ways to control the magnetisation of a medium by means other than magnetic fields. The control of magnetism by light is one of the promising approaches to this problem, since a laser pulse is one of the shortest ever man-made events.

There is no doubt that recent progress in the development of compact ultrafast lasers, the successful introduction of lasers into magnetic storage technology as well as enormous breakthrough in the understanding of spin-dependent phenomena in solids will further spur the realisation of ultrafast magnetisation reversal in storage and spintronics devices. Nevertheless, there are still many fundamentally intriguing issues to be answered on the way to real applications of opto-magnetic phenomena and a 'THz opto-magnetic revolution' in magnetic recording and information processing.

The aim of the proposed research was to develop 'opto-nano-magnetism' that is, the manipulation of the magnetic properties of nanomagnetic materials using (magneto-) optical effects, as a novel approach for future magnetic recording and information processing technology. This topic is situated at the junction of coherent nonlinear optics, nanophotonics and magnetism. In particular, we investigated the effects of light on magnetic order at the nanoscale, optimise materials and conditions for highly efficient and ultrafast (10-12 seconds and faster) optical control of nanomagnets and in this way tried to initiate a development of novel technology for unprecedented fast (THz) magnetic recording and information processing.

The project had the following objectives:
- obtain fundamental knowledge on ultrafast opto-nano-magnetism and ultrafast magnetisation dynamics at the nanoscale (understanding laser-induced magnetization reversal in nanomagnets smaller than 300 nm);
- achieve highly efficient nanolocalisation of magnetism (laser-induced magnetisation reversal faster than 100 ps and with spatial resolution below 300 nm);
- develop novel approaches for truly ultrafast femtosecond laser control of nano-magnetism (switching of nanomagnets faster than 1 ps);
- initiate developments of novel technologies for unprecedented fast THz magnetic recording and information processing, including spintronics (developing the conceptual design of ultrafast recording and spintronics devices).

After 36-months performance of the project we have achieved most of the objectives planned. In particular,
- Novel mechanisms and approaches of magnetisation reversal at sub-100 ps time-scale in continuous films and structures with size down to 200 nm have been discovered and theoretical understanding has been vastly improved.
- Novel approaches for laser control of nanomagnetism at the picosecond time-scale which could not be even predicted before were discovered.
- Knowledge accumulated in the project has been transferred to industries. Seagate and Philips have analysed the future of the opto-magnetic technology in commercial devices suggesting a conceptual design for opto-magnetic read-head and required picosecond laser. NXP sees no product application for spintronic devices in their future development because of strategic changes in the company. All-optical switching has made it to the roadmap of the HDD industry, as the next technology after HAMR. The consequence would be that a production of 400 million lasers each quarter to be incorporated in write heads. According to an analysis of Philips, this is potentially doable.