Frontier of Quantum Molecular Spintronics Based on Single-Molecule Magnets: Who is greater, Nomo or Ichiro ?
山下 正廣 教授
Spintronics is a key technology in 21st century based on the freedoms of the charge and spin of the electron. The MRAM systems by using Giant Magnetoresistance (GMR) or Tunneling Magnetoresitance (TMR) have several advantages such as no volatility of information, the high operation speed of nanoseconds, and the high information memory storage density. Usually in these systems, the bulk or classical magnets are used, while in our study we will use Single-Molecule Magnets (SMMs), which are usually composed of multi-nuclear metal complexes and nano-size magnets. In our study, we hope to realize the new quantum molecular spintronics such as GMR and TMR by using SMMs.
According to such a strategy, we have synthesized the conducting SMM such as [TbPc2]Cl>0.6. The hysteresis is observed below 10K. This SMM shows the negative magnetoresistance below 8 K. As for the second strategy, we try to input/output one memory into/from double-decker Tb(III) SMM (TbPc2) by using the spin polarized STM. In this research, we have observed Kondo peak by using STS (Scanning Tunneling Spectroscopy) for the first time. We have succeeded in controlling the appearance and disappearance of Kondo peak by the electron injection using STS, reversibly. This is considered as the first single-molecule memory device. As for the third strategy, we have made the FET (Field Effect Transistor) devices of SMMs. The DyPc2 device shows the ambipolar (n- and p-type) behavior, while the TbPc2 device shows the p-type behavior. As for the fourth strategy, we have made doping of Cs atoms onto Pc2Y, where Kondo peaks have not observed by coupling between the radical of Pc and 6s electron of Cs atom to make a single pair, while other Pc2Y sites show Kondo peak due to the radicals. As for the fifth strategy, we have succeeded to write the letters of T and U, which are the initials of Tohoku University. As for the sixth strategy, we have evaporated TbPc2 SMM on the magnetic Co surface, and by using the magnetic Cr tip, we have observed the GMR (200 %) for the first time. Finally, we have evaporated the Co film and TbPc2 on Au surface, and by using the magnetic Cr tip, we have observed the TMR with the double butterfly structure for the first time.
 T. Komeda, M. Yamashita, et al., Nature Commun., 2, 217(2011)