How to synthesize nanomagnetic fluid

Using agate mortar, crush Chloride crystals of two metals, say cobalt chloride and iron chloride into fine powder. Put the fine crystals in a beaker and add distilled water so that we obtain a concentrated solution. Using high energy ball milling apparatus, ball mill it for 2 hours in a 650 rotations per minute speed. Add potassium hydroxide solution until it become brown. If it is not becoming brown, add a few drops of concentrated sodium hydroxide. The solution is subjected to heating till it boils. Let it remain there for 2 minutes. Ball milling shall repeated to 3 hours in a 600 rpm speed now. Filter the liquid and residue be dried using oven. Dried samples are heated to 773 K using a quality furnace. Put water, oleic acid and paraffin liquid in equal amount and ball mill it for 10 hours in a relatively low rpm (250 rpm enough). The resultant fluid is nanomagnetic and very much useful.