Dual-shot dynamics and ultimate frequency of all-optical magnetic recording on GdFeCo

Although photonics presents the fastest and most energy-efficient method of data transfer, magnetism still offers the cheapest and most natural way to store data. The ultrafast and energy-efficient optical control of magnetism is presently a missing technological link that prevents us from reaching the next evolution in information processing. The discovery of all-optical magnetization reversal in GdFeCo with the help of 100 fs laser pulses has further aroused intense interest in this compelling problem. Although the applicability of this approach to high-speed data processing depends vitally on the maximum repetition rate of the switching, the latter remains virtually unknown. Here we experimentally unveil the ultimate frequency of repetitive all-optical magnetization reversal through time-resolved studies of the dual-shot magnetization dynamics in Gd 27 Fe 63.87 Co 9.13 . Varying the intensities of the shots and the shot-to-shot separation, we reveal the conditions for ultrafast writing and the fastest possible restoration of magnetic bits. It is shown that although magnetic writing launched by the first shot is completed after 100 ps, a reliable rewriting of the bit by the second shot requires separating the shots by at least 300 ps. Using two shots partially overlapping in space and minimally separated by 300 ps, we demonstrate an approach for GHz magnetic writing that can be scaled down to sizes below the diffraction limit. Optical magnetization: extreme limits for magnetic data recording with light The potential for combining the speed of photonics with the advantages of magnetic data storage, using pulsed laser light to control the magnetization of alloys of gadolinium, iron and cobalt (GdFeCo), has been explored and quantified. Achieving ultrafast and energy-efficient optical control of magnetism could revolutionize information-processing technology. Researchers led by Xiangping Li at Jinan University in China and Alexey V. Kimel at Radboud University in The Netherlands have experimentally determined the fastest possible rate of the optical reversal of magnetization achieved by this promising new technology. They suggest data switching repetition rates of up to three billion cycles per second (3 GHz) are feasible. They also propose a method to achieve spatial resolution of data recording at scales below light’s ‘diffraction limit’, which is generally believed to restrict the attainable resolution.