Preparation and magnetic performance of the magnetic fluid stabilized by bi-surfactant

► The oleic acid coated Fe3O4 nanoparticles are functionalized with polyisobutylene succinimide. ► The poly alpha olefin oil based magnetic fluid is obtained by phase-transfer method. ► The magnetic fluid is stable and superparamagnetic. ► The magnetic fluid exhibits well oil disperse characteristic. ► The magnetic fluid can be widely used in loudspeaker.