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.