Crystallographic, thermal and magnetic properties of CoCl₂-graphite intercalation compound - a quasi-two-dimensional system of finite size clusters

From the susceptibility and heat capacity measurements, the second stage CoCl₂-graphite intercalation compound (GIC) is proved a good example of a two-dimensional XY-like ferromagnet. It is directly revealed by electron microscopy that each CoCl₂ plane is not extended infinitely but composed of many island-like clusters of finite size. The importance of the latter is discussed and it is concluded that the characteristic lattice structure is responsible to the successive nature of ordering in the present system.