Development of Magnetoresistive Halfmetals and Halfmetallic Composites for Spintronics

我们为期三年的项目专注于半金属（HM）氧化物材料，这些材料是具有100%自旋极化载流子的铁磁体（在理想情况下）。这种材料形成了隧道型磁阻（TMR）器件的基础，其应用发现于目前新兴的称为自旋电子学的新技术中。在迄今发现的少数几种HM材料中，B位有序双钙钛矿（DP）氧化物A_2B 'B“O_6，包括原型Sr_2FeMoO_6化合物，是最有希望用于室温（RT）低场（LF）应用的候选材料。B位有序的DP也在本项目中发挥核心作用，尽管相关的钙钛矿衍生系统也进行了研究。该项目的目标是通过控制这些材料的内在和外在材料特性来寻找这些材料作为RT-LF-TMR材料的极限。研究内容包括以下几个方面：（i）Sr_2FeMoO_6及其相关DP氧化物的原子级本征特性的定制（ii）通过选择合成条件控制晶粒/磁畴的尺寸（iii）设计复合结构以增强RT-LF TMR特性（iv）在钙钛矿氧化物中寻找新型HM化合物我们独特的（新）材料设计和定制方案本身，包括各种本征和非本征材料参数的原子到宏观尺寸的操纵，被证明是非常成功的。我们坚信，我们的方法在未来也将被发现是有用的，可以为各种前沿材料实现更有组织和更高效的设计方案。

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.