Magnetic field-induced phase transitions in ferrofluid emulsion

Two field-induced phase transition regimes are found in a ferrofluid emulsion system, which are defined by three critical fields, H-c1 < H-c2 < H-c3. The first regime, which starts at H-c1 and finishes at H-c2, is the transition from a gas to induced Nematic liquid crystal phase. In the second regime, or H-c2 < H < H-c3, induced Nematic liquid crystal transits to columnar solid structure. A phase diagram is drawn and is explained well by a scaling calculation, which gives H(c1)similar to Phi(-1/2), H(c2)similar to Phi(-1/4), and H(c3)similar to Phi(gamma) exp(pi G/Phi(gamma/2)), where Phi is the volume fraction, gamma=0.172 and G=1.44.