[Summary] A research group led by Dr. Jun-ichiro Ohe, and Professor Sadamichi Maekawa at Institute for Materials Research, Tohoku University has developed a new computer simulation method for magnetic semiconductors in collaboration with a group led by Assistant Professor Kazuma Nakamura and Associate Professor Ryotaro Arita at Graduate School of Engineering, University of Tokyo. The new method makes it possible to precisely analyze magnetic properties including the electron-electron interaction in materials. The newly developed method has improved theoretical analyses of magnetic semiconductors. Although ferromagnetic semiconductors have been made only at low temperatures, the new method is expected to design materials for magnetic semiconductors that show ferromagnetic properties at high temperatures, and to contribute to application of spintronics devices. [Details] Appliances in ordinary lives include numerous electronic devices. General devices are divided into two types; one uses electric properties (electric charge) such as transistor, and the other uses magnetic properties (spin) such as hard discs. Spintronics that uses both electric and magnetic properties in one device has recently been proposed. Industries and universities have conducted researches on this field in the world. Magnetic semiconductors for materials to realize spintronics devices have gathered attention. Although semiconductors do not have magnetic properties, they have both electric and magnetic properties by adding magnetic atoms as an impurity to increase electric conduction. To use magnetic properties in the device, magnet directions of the impurities are required to point to the same direction (ferromagnetic coupling.) Some magnetic semiconductors that show ferromagnetic bond have been reported. To realize ferromagnetic coupling requires to cool the device at -130℃ (Curie temperature.) However, the device can not operate at such a low temperature, and semiconductors that show ferromagnetic coupling at high temperatures is essential. It is important to predict promising materials for magnetic semiconductors by theoretically understanding the cause of ferromagnetic property because conducting experiments on each material takes immeasurable costs and time. One of prediction methods of magnetic properties is material simulations by using a computer. When discussing magnetic properties in materials, it is important to know whether electrons stay in orbit localized close to nucleus, or electrons extends in the sample. When electrons localize, repulsion between electrons becomes important, and causes complicated problems. Existing computer simulations have used approximation to treat repulsion between electrons. When one try to treat the repulsion precisely, it has been difficult to design materials because the material must be mapped into the simple model. In this study, the research group has proposed two types of methods to overcome the difficulty. One is density functional theory that describes materials, but uses an approximation to treat repulsion. The other is quantum Monte Carlo method that can precisely treat repulsion, but be applied only to easy models. The newly developed method calculates quantum Monte Carlo method by practical parameter acquired by density functional formalism, which makes it possible to describe magnetic semiconductors. The group has calculated ferromagnetic semiconductors (Ga,Mn)As, and got good agreement with experiments. The research results show that long-distance ferromagnetic coupling between two magnetic impurities became stronger as the temperature decreasing, and that the new method is a reliable method to analyze magnetic semiconductors. The research results have been chosen as a noteworthy article of the August, 2009 issue of “Journal of the Physical Society of Japan.” The paper’s title is _Combined Approach of Density Functional Theory and Quantum Monte Carlo Method to Electron Correlation in Dilute Magnetic Semiconductors._ [Contact] Professor Sadamichi Maekawa Institute for Materials Research, Tohoku University TEL: +81 22-215-2005, FAX: +81 22-215-2006 E-mail: maekawa@imr.tohoku.ac.jp