Study of magnetisation behaviours for binary ionic ferrofluids

The magnetisation curves of ionic fluids of three types (CoFe 2 O 4 ferrofluids, p-NiFe 2 O 4 paramagnetic fluids and CoFe 2 O 4 -p-NiFe 2 O 4 ferrofluids prepared by Massart method) are measured at room temperature and their magnetisation behaviours are studied. Comparison of the experimental data of CoFe 2 O 4 ferrofluids with the Langevin theory curve demonstrates a considerable difference between them, but the curve fitted by model of a gas-like compression agrees with experimental data very well. The experimental results show that the magnetisation of the CoFe 2 O 4 -p-NiFe 2 O 4 binary ferrofluids is larger than the sum of the magnetisation of the two single ferrofluids in high field. The magnetisation behaviour of the binary ferrofluids is explained by self-assembled ring-like aggregates of CoFe 2 O 4 ferrofluids particles breaking.