March 23 (Fri), 2012, 1:30~2:30 pm
Prof. Masahiro Yamashita
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Japan
“Quantum Molecular Spintronics Based on Single-Molecule Quantum Magnets Composed of Multiple-Decker Pthalocyaninato Ln(III) Complexes”
Place: Rm# 310, Chemistry Bldg. 3
All are cordially invited to attend the talk.
Spintronics is a key technology in 21st century based on the freedoms of the charge, spin, as well as orbital of the electron. The MRAM systems (magnetic random access memory) by using GMR, CMR or TMR have several advantages such as no volatility of information, the high operation speed of nanoseconds, the high information memory storage density, and the low consuming electric power. Usually in these systems, the bulk magnets composed of the transition metal ions or conventional magnets are used, while in our study we use Single-Molecule Quantum Magnets (SMMs), which are composed of multi-nuclear metal complexes and nano-size magnets, and moreover show the slow relaxations with the double-well potential defined as |D|S2 and the quantum tunneling. Although the bulk magnets are used in GMR which have the largest spin quantum number of 5/2, we can create the artificial spin quantum numbers of 10, 20, 30, 40 in SMMs. Therefore, we can anticipate the new quantum GMR in this system by using SMMs..
According to such a strategy, we have synthesized the conducting SMM such as [Pc2Tb]Cl0.6, whose blocking temperature is 47K. The hysteresis is observed below 10K. This conducting SMM shows the negative magnetoresistance below 7K, which is the first observation in the conducting SMMs.
As for the second strategy, we have a plane of the input and output of one memory in double-decker Tb(III) SMM (Pc2Tb) by using the spin polarized STM (Scanning Tunneling Microscopy). In this research, we have observed Kondo Effect at 4.8 K 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.1
As for the third strategy, we have made the FET (Field Effect Transistor) devices of SMMs. The Pc2Dy device shows the ambipolar (n- and p-type) behavior, while the Pc2Tb device shows the p-type behavior. Such a difference is explained by the energy levels of the lanthanide ions.2
 T. Komeda, M. Yamashita, et al., Nature Commun., 2011, 2, 217
 K. Katoh, M. Yamashita, et al., J. Am. Chem. Soc., 2009, 131, 9967