Half-metallic ferromagnets prepared by topochemical insertion of lithium into W-based cation-deficient perovskite oxides

Spin-polarised conducting materials are an essential part of any future spintronic device. Currently there are very few, if any materials which fulfil this role. We have been investigating the preparation of Half-Metallic Ferromagnetic Materials (HMFM) which exhibit spin-polarised conductivity, via the lithiation of cation-deficient A4MW2O12 (A = La, Sr, Ba; M = Fe, Mn) perovskite phases. Magnetisation data indicate the lithiation of these materials can induce ‘ferromagnetic’ behaviour – a necessary prerequisite for HMFM behaviour – and measurements are underway to investigate the electronic transport behaviour of these materials. We propose to collect neutron powder diffraction data from these materials to investigate their crystal structures, especially a subtle cation disordering that appears to occur on lithium insertion. We also wish to collect diffraction data to determine their ordered magnetic structures to determine if they are ferromagnetic or ferrimagnetic – an important distinction with respect to HMFM behaviour.

自旋极化导电材料（spin-polarised conducting materials）是未来所有自旋电子学（spintronic）器件不可或缺的组成部分。目前几乎没有（即便有也极少）能够满足该应用需求的此类材料。我们团队长期致力于通过阳离子缺陷型A4MW2O12（A=La、Sr、Ba；M=Fe、Mn）钙钛矿相的锂化反应，制备具备自旋极化导电特性的半金属铁磁材料（Half-Metallic Ferromagnetic Materials, HMFM）。磁化测试数据表明，对这类材料进行锂化处理可诱导出“铁磁性”行为——这是半金属铁磁材料特性的必要前置条件。目前我们正开展相关测试，以探究这类材料的电子输运行为。我们计划采集这类材料的中子粉末衍射（neutron powder diffraction）数据，以解析其晶体结构，尤其是锂嵌入过程中疑似出现的细微阳离子无序现象。此外，我们还希望通过衍射数据确定其有序磁结构，以此判断材料属于铁磁性还是亚铁磁性——这对半金属铁磁材料的性能判定具有至关重要的区分意义。