Combinatorial Search for Transparent Oxide Diluted Magnetic Semiconductors
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Combinatorial Search for Transparent Oxide Diluted Magnetic Semiconductors T. Fukumura and M. Kawasaki a Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan Zhengwu Jin, H. Kimura, Y. Yamada, and M. Haemori Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502, Japan Y. Matsumoto, K. Inaba, M. Murakami, R. Takahashi, and T. Hasegawa a Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan H. Koinuma a,b Frontier Collaborative Research Center, and Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan a Combinatorial Materials Exploration and Technology (COMET), Tsukuba 305-0044, Japan b CREST, Japan Science and Technology Corporation, Tokyo 169-0072, Japan ABSTRACT Diluted magnetic semiconductor (DMS) possesses charge and spin degrees of freedom leading to their interplay promising for novel devices. DMSs based on II-VI and III-V compound semiconductors have been extensively studied so far. Recently, the oxide semiconductors doped with transition metal magnetic impurity have attracted much attention for the possible high ferromagnetic Curie temperature. Here, we overview recent studies of the transparent oxide based DMSs, ZnO, TiO2, and SnO2 doped with 3d transition metals, by using the combinatorial materials synthesis and the high throughput screening. INTRODUCTION Diluted magnetic semiconductor (DMS) is the semiconductor injected with spin as a new degree of freedom, and is expected to be a promising candidate material for next generation devices utilizing the spin controlled by light and charge carrier. The study of II-VI compound semiconductor based DMSs has been continued over twenty years [1]. The Mn ion has been often used as a spin injector yielding giant magnetoresistance and magnetooptical effect, the latter of which is used for the practical application of (Cd,Mn)Te as an optical isolator. Although several tens of molar percents of Mn can be doped into II-VI semiconductors, the n-type carrier concentration is 1019 cm-3 in maximum and the p-type carrier doping is difficult. These drawbacks result in the rather low ferromagnetic Curie temperature in the order of ~1 K [2], that is well explained by the carrier induced mechanism [3]. On the other hand, III-V semiconductor GaAs doped with only 5 mol% of Mn has the Curie temperature as high as 110 K due to strong p-d exchange interaction intermediated by mobile holes [4]. Furthermore, the light induced ferromagnetism [5], the injection of polarized spin into semiconductor [6], and the modulation of Curie temperature by field effect [7] have been demonstrated. For the practical use of room temperature devices, however, the ferromagnetic Curie temperature over room temperature is needed. Recently, various novel ferromagnets have been reported [8-11] so that further progress in this field is expected. Although oxide semiconductors have been studied for a long time, they have scarcely been regarded as a host of DMS proba
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