An international team of researchers affiliated with Göttingen University has found a way to store vast amounts of data – up to one petabyte – per square inch. One petabyte is equivalent to 1,000 terabytes or one million gigabytes. Using information stored in the spin of an electron, the scientists succeeded in storing the information in an organic molecule and reading it at a temperature close to room temperature.
Elementary particles, many atomic nuclei and atoms with certain electron configurations have what is called spin, defined as the rotation of a body around its own axis. This enables an alternative form of electronic data processing – called “spin electronics or spintronics.” The scientists developed a unique molecule that serves as the memory for their electronic device: They fused non-magnetic carbon atoms linked to one another in three benzene rings into one unit. Using spin injection, they chemically added an unpaired electron that carries a net spin. This can be exploited to store information as “0” and “1” by having the electron’s spin orientated up or down. Another accomplishment of the researchers was to use a magnetic reference electrode to read out the stored information at room temperature.
“Spin storage on an organic material and the successful reading at room temperature represent a breakthrough in organic spin electronics,” emphasised Prof. Markus Münzenberg, one of the physicists from Göttingen. “Spintronics integrated into flexible plastic components are already a familiar part of the organic LEDs employed in today’s displays, TV screens and smartphones. Our recently developed molecular units have a similar potential.”
Interface magnetoresistance effect. Molecular structure of zinc methyl phenalenyl (ZMP) in a neutral state with no net spin (top). Charge transfer processes through hybridization on the ferromagnet surface can change the chemical state.
The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices opening avenues for developing multifunctional molecular spintronics. Such ideas have been researched extensively, using single-molecule magnets and molecules with a metal ion or nitrogen vacancy as localized spin-carrying centres for storage and for realizing logic operations. However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task. In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl, have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets. Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development.