Development of Magnetoresistive Halfmetals and Halfmetallic Composites for Spintronics

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Our three-year project was focused on halfmetallic (HM) oxide materials that are conducting ferromagnets with 100 % spin-polarized carriers (in an ideal case). Such materials form the bases for tunneling-type magnetoresistance (TMR) devices application of which is found in the presently emerging new technology called spintronics. Among the handful of HM materials discovered so far, B-site ordered double-perovskite (DP) oxides, A_2B'B''O_6, including the prototype Sr_2FeMoO_6 compound are the most promising candidates for room-temperature (RT) low-field (LF) application. The B-site ordered DPs were also in the central role in the present project, though related perovskite-derived systems were investigated as well. The goal of the project was to search for the limits of these materials to function as RT-LF-TMR materials by means of controlling their intrinsic and extrinsic material characteristics. The research included the following aspects:(i) Tailoring of atomic-level intrinsic characteristics of Sr_2FeMoO_6 and related DP oxides(ii) Control of the size of grains/magnetic domains by the choice of synthesis conditions(iii) Design of composite structures to enhance the RT-LF TMR characteristics(iv) Search for novel HM compound(s) among perovskite oxidesOur unique (new) material design and tailoring scheme itself, comprising atomic-to-macroscopic dimensional manipulation of various intrinsic and extrinsic material parameters, turned out to be highly successful. We positively believe that our approach will be found useful in future too to achieve a more organized and highly productive design scheme for a wide range of frontier materials.