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Research Results

2011 |

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Nov. 2011

 Crystal physics group (Assoc. Prof. Noritaka Usami, Dr. Wugen Pan et al.) has successfully implemented nanostructures to consist of photonic crystals and quantum dots in crystalline silicon solar cells, and demonstrated that the nanostructures can improve the conversion efficiency of solar cells. To our knowledge, this is the first to show that quantum dots can improve the performance of practical solar cells. The newly developed solar cells can be also used to study controlling mechanisms of the conversion efficiency of solar cells with quantum dots, and will contribute to the deep understanding of physics toward realization of ultra-high-efficiency solar cells. These achievements were reported in Nikkei-Sangyo Shimbun (November 1, 2011), and will be presented as an invited talk at 2012 spring meeting of Japan Society of Applied Physics. Further research and development on this topic will be funded by JST-ALCA.

Aug. 2011

 A research group led by Ph. D. Student Ken-ichi Uchida and Professor Eiji Saitoh at Institute for Materials Research, Tohoku University has discovered a new method to generate spin current through acoustic wave injection.
  In recent years, more and more approaches to the environmental and energy issues have been taken, and it is required to develop clean and reliable energy sources and power-saving electronic devices. Spintronics, the new electronic technology which actively exploits spin freedom of electrons, is expected to develop novel drive principles of electric and magnetic devices and to save energy of them. Therefore, a lot of research on spintronics has been conducted all over the world. However, although most of the spintronics functions are driven by "spin current", the generation methods of spin current are very limited.
 In this study, we have discovered the new method to generate spin current only through the acoustic wave injection. This method enables us to extract electric and magnetic energy even from nonmagnetic insulators, which are used only as substrates of the devices. This achievement is expected to contribute the improvement of the degrees of freedom for spintronics device design and the development of next-generation energy-saving electronic technology with a very low impact on the environment.
 This research has been partly conducted in collaboration with Japan Atomic Energy Agency(JAEA), Graduate School of Engineering, Tohoku University and University of Keiserslautern (Germany), as part of the CREST program of JST.

Jun. 2011

 A research group led by Assistant Professor Kazuya Ando and Professor Eiji Saito at Institute for Materials Research, Tohoku University, and Director Sadamichi Maekawa at Advanced Science Research Center of Japan Atomic Energy Agency has discovered a novel spin injection method which can be enhanced to all kinds of materials.

 Recently, spintronics has been expected as an energy-saving electronic information technology. In spintronics, spin current which means magnetic current of electrons is utilized, instead of electric current. Development of versatile spin injection method available into all types of materials is the most critical task for realization of next-generation spintronics devices, such as quantum computers and very low power consumption information-processing devices. However, it is not easy to produce spin current. Because of physical constraints, spin current could be injected only into very limited types of materials.

 In this study, the research group has developed an extremely versatile spin injection method that is not subject to any physical constraints, by utilizing magnetic dynamics. In addition, the research group has revealed that the method can be controlled by electric field, and has successfully produced 1,000 times larger spin current than that by conventional method.

 The research results enable high-efficiency spin injection into not only metals, but also semiconductors, organic substances, and high-temperature superconductors with ease, and offer design of spintronics devices greater latitude. It is expected to contribute to next-generation energy-saving electronics with a very low impact on the environment.

Jun. 2011
  Institute for Materials Research, Tohoku University, RIKEN, Institute for Solid State Physics, University of Tokyo, and Japan Atomic Energy Agency (JAEA) have developed a spintronic device consisting of a nonmagnetic nanowire (Ag) and two ferromagnetic wires separated by magnesium oxide layers. This enables efficient spin injection and spin accumulation in silver with over 100-fold higher output voltage due to large spin accumulation, which is the highest value in the world. This achievement has been acquired by Assistant Professor Saburo Takahashi at Institute for Materials Research, Tohoku University, in collaboration with Team Leader Yoshichika Otani and Deputy Team Leader Yasuhiro Fukuma at Quantum Nano-Scale Magnetics Team, RIKEN Advanced Science Institute, and Director Sadamichi Maekawa at Advanced Science Research Center of JAEA.
  The research results have been published online in Nature Materials on June 12, 2011.
May. 2011
  Tohoku University, Japan Synchrotron Radiation Research Institute (JASRI), and Institute for Solid State Physics, University of Tokyo, have succeeded in the world first soft X-ray spectroscopy under very high magnetic fields of 21 Tesla (= 210,000 gauss) at the beam line BL25SU of SPring-8. The developed system realizes magnetic analysis by Soft X-ray Magnetic Circular Dichroism (MCD) on any of magnetic materials for practical use, including strong rare earth magnets. It would be useful to examine the role of rare-earth elements such as Dysprosium in the magnet and to find out some ubiquitous elements for replacement of expensive ones. The collaboration research has been represented by Associate Professor Yasuo Narumi at Tohoku University, Senior Researcher Tetsuya Nakamura at JASRI, and Koichi Kindo at University of Tokyo. The results have been published online in Applied Physics Express (APEX) on May 24, 2011. The paper's title is "Soft X-ray Magnetic Circular Dichroism of a CoFe/MnIr Exchange Bias Film under Pulsed High Magnetic Field".