Visualized effects of oxidation and temperature on vortex-state fe3O4 particles examined by environmental TEM and off-axis electron holography - Almeida,TP; Muxworthy,AR; Williams,W; Kasama,T; Hansen,TW; Brown,PD; Kovács,A; Dunin-Borkowski,RE (Microscopy and Microanalysis, 2018)