Study of magnetisation behaviours for binary ionic ferrofluids

The magnetisation curves of ionic fluids of three types (CoFe2O4 ferrofluids, p-NiFe2O4 paramagnetic fluids and CoFe2O4–p-NiFe2O4 ferrofluids prepared by Massart method) are measured at room temperature and their magnetisation behaviours are studied. Comparison of the experimental data of CoFe2O4 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 CoFe2O4–p-NiFe2O4 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 CoFe2O4 ferrofluids particles breaking.