High Throughput Optimization of Y-Type Magnetoplumbite Epitaxial thin Film Growth by Combinatorial Pulsed Laser Depositi
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HIGH THROUGHPUT OPTIMIZATION OF Y-TYPE MAGNETOPLUMBITE EPITAXIAL THIN FILM GROWTH BY COMBINATORIAL PULSED LASER DEPOSITION TECHNIQUE I.Ohkubo1, Y.Matsumoto1, M.Ohtani1, T.Hasegawa1, K.Ueno2, K.Itaka3, A.Parhat3, T.Chikyow3, M.Kawasaki3.4 and H.Koinuma1.3.5 1 Materials and Structures Laboratory, Tokyo Institute of Technology 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan 2 Central Technology Laboratory, ASAHI KASEI CORPORATION, 2-1 Samejima, Fuji, Shizuoka, 416-8501 Japan 3 COMET-NIMS, 1-1 Namiki, Tsukuba, Ibaraki,305-0044, Japan 4 Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan 5 Frontier Collaborative Research Center Tokyo Institute of Technology 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan and CREST-Japan Science and Technology corporation, 3-4-1 Ohkubo, Japan ABSTRACT Thin films of Y-type magnetoplumbite (Ba2Co2Fe12O22 : Co2Y) with such a huge unit cell length as 43.5 Å has been successfully fabricated for the first time with the aid of combinatorial optimization of pulsed laser deposition process. Planning a thickness gradient CoO buffer layer on MgAl2O4(111) substrate was very effective for prevent the phase separation of Co deficient impurity (BaFe2O4) to reside in the formation of desired Co2Y phase. From the TEM analysis, the CoO buffer layer of optimum thickness was incorporated into the Co2Y film to make the interface with the make an atomically sharp. INTRODUCTION One of the keys for miniaturization of electronic devices is the magnetic components. For this aim, much attention has been paid to micromagnetic devices using thin film inductors or transformers operable at high frequencies [1]. Soft magnetic films with excellent characteristics in a high frequency region are strongly desired as core materials. Y-type magnetoplumbite is known as one of the candidates for the core materials in micro inductor and other microwave devices operable at the frequency of GHz. Magneoplumbite is a hexagonal ferrite that has many crystal structures denoted as M, Y, Z, W, X and U [2]. All these magnetoplumbite phases can be recognized as natural superlattices with sequential stacking of three different structural blocks of S, R and T along the c-axis. S block has the chemical formula of (MeFe2O4)2 and the same structure as [111] direction of cubic spinel crystal structure. The face centered closed-packed structure (FCC) has the vertical sequence of ABCABC- oxygen planes ([0001], c-axis direction)(Fig.1). R (BaFe9O15) and T (BaFe4O7) blocks have hexagonal closed-packed structure, with the vertical sequence of ABABfor both composed of oxygen and barium atoms ([0001], c-axis direction). Y-type magnetoplumbite has a unit cell composed of STS*T*ST blocks , where * indicates the structure rotated by 180° around the c-axis, to form the modulated closed-packed structure that can be described as ABCBCBCAB····(Fig.1). Because of such a huge c-axis lattice parameter (43.5Å) and resulting large crystal magnetic anisotropy, Y-type magnetoplumbite has an excellent frequency characteristics of the
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