Around 1900, it became possible to store information on magnetic wires and tapes, and this development finally paved the way for modern day computers. With the advent of personal computers and related devices, such as mobile telephones, our world has become highly technology-oriented and data storage has become digitalized. One of the challenges in the highly technological world that we live in is saving large amounts of information in the digital form. This fact becomes clear if we look at the exponential growth in digitally stored information that we have experienced in the past decade and a half. Whereas until about 15 years ago storing information on paper and other analog forms was still common, we are now fast approaching a time of “total digitalization”. The need to store such large amounts of data necessitates the improvement of the amount of information that can be stored per unit of space. Hence miniaturization is an essential goal in data storage devices in particular, and the electronics industry in general.
Storing Information in Molecules
Current magnetic data storage devices rely on saving information on metal oxide particles. However, their magnetization becomes unstable when the particles are made too small, and hence there is a physical limit to their miniaturization. One of the smallest units where information can be envisaged to be stored are molecules. The first breakthrough in that direction appeared with the observation in the early 1990s that a certain molecular cluster containing twelve manganese ions displays magnetic bistability and can thus in principle act as a molecular data storage medium . Follow-up analyses of the physical properties of this cluster showed that the magnetic moment and the magnetic anisotropy are the important parameters that control the energy barrier that leads to magnetic bistability in these molecules. Soon after the development of this intriguing molecular cluster and the analyses of its properties, it was realized that increasing the magnetic moment of the system by chemically synthesizing larger clusters is comparatively easy.
Hence, most research efforts in the two decades following the initial discovery largely focused on increasing the magnetic moment of such molecular systems . However, it was found that with increasing magnetic moment, the magnetic anisotropy decreases and hence the energy barrier remains small . In the last decade, the focus has thus shifted to ions with large magnetic anisotropies. This approach has already delivered positive results and simple molecules containing only one metal ion are now known to possess large energy barriers . Thus, these molecules may be employed for information storage. Indeed, we have recently shown that a simple cobalt complex with only one cobalt ion shows a large energy barrier and, importantly, magnetic bistability, making it a unique candidate in this field of research .
Despite the progress in developing molecules for data storage devices, challenges remain. Thus, the temperature at which such systems work is still low. Target-oriented synthesis of relevant molecules and a thorough investigation of their physical properties will deliver a solution to this problem. The incorporation of these molecules into real devices is another challenge and the reading and writing of information at the molecular level still remains a critical question. Thus, success in this extremely attractive field of research depends on bringing together the expertise of chemists, physicists and engineers. With the recent path breaking discoveries that have been made in the field, its future is certainly very bright: We might soon be able to store 1000-fold more information per unit space as compared to what is now possible.
Prof. Dr. Biprajit Sarkar
Institut für Chemie und Biochemie
Freie Universität Berlin
Prof. Dr. Joris van Slageren
Institut für Physikalische Chemie
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