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. 2016 Mar 16;6:23254. doi: 10.1038/srep23254

Figure 1. Characterisation of intercalated graphene laminates.

Figure 1

(a–d) Optical photographs of pristine (scale bar 1 cm) and K-, Cs- and Ca- intercalated GLs (scale bar 1 mm), respectively. Li-GL (not shown) has a similar colour to Ca-GL. (e) Temperature dependence of ZFC and FC mass magnetisation, M, for Li-GL (red symbols) and Ca-GL (black) at H = 4 Oe applied parallel to the laminates’ surface. The estimated systematic error in determining M is ~10% due to inaccuracy of measuring the sample mass that was typically several mg (this is difficult because of the extreme sensitivity of intercalated GLs to moisture and oxygen). The inset shows a zoom-up of the M(T) curve for Ca-GL. (f) Main panel: ZFC and FC M(T) at different H for Ca-GL. The inset shows the magnetisation dependence as a function of H ‖ ab at 1.8 K, which is characteristic of type-II superconductors with significant trapping of magnetic flux (pinning). The particularly strong flux trapping (very small FC Meissner response) is likely to be due to the fact that our laminates are made up from thousands of individual graphene crystallites, with inevitable voids between them.