Field-induced first-order phase transition and spinodal point in nematic liquid crystals

We report the discovery of a novel, magnetic-field-driven first-order phase transition in nematic liquid crystals. The transition is between a spatially periodic distortion, stable at intermediate field strengths, and a uniform distortion which is the ground state at high fields. From studies of dynamics we show that the transition is first order. We also find a spinodal point, below which the transition from the uniform to the periodic state occurs continuously. We discuss the utility of thickness gradient samples and determine the equilibrium wavelength of the periodic phase as a function of magnetic-field strength.