Under normal condition & absence of external magnetic field, magnetic fluid becomes thermodynamically unstable. Hence magnetic dipole moment of each particle is randomly oriented and there is no resultant moment observed. So under normal condition & absence of external magnetic field, magnetic fluid behaves just like an ordinary fluid.

When magnetic fluid is placed under the influence of an external magnetic field, the dipole moment of each particle tends to align in the direction of an external magnetic field. So there is a large magnetic moment induced inside the medium. Therefore the fluid has net resultant magnetization. So under the influence of external magnetic field, the fluid exhibit several apparently looking like magical phenomena like defying gravity, levitation of non-magnetic object immersed in the fluid, spontaneous formation of spike, self levitation of magnets (in absence of other externally applied magnetic field. When it subjected to an external magnetic field, it exhibits large magnetization and when the field removed, the magnetic fluid instantaneously attains its zero magnetic state.

Temperature Sensitive Magnetic Fluid:
Ferro fluids usually available in market contain magnetite as nanoparticles; such fluids have high Curie temperature and low paramagnetic coefficient. We have synthesized fluids which have low Curie temperature (<70 °c) and have high paramagnetic coefficient. These fluids may find application in energy conversion devices, transformer oil cooling etc.