Effect of bulk magnetic field on critical Ising films

Two-dimensional Ising films L x infinity in a nonvanishing bulk magnetic field H are studied at the bulk critical temperature Tc for two choices of surface fields (a) H1 = HL = 0 (ordinary transition), and (b) H1 = HL = infinity (normal transition) by the density-matrix renormalization-group method. Universal scaling functions for magnetization profiles, the excess magnetization gamma, the longitudinal correlation length xi parallel, and for the analog of the solvation force fsolv are found and discussed. When H1 = 0 the scaling function for fsolv has two symmetric minima at y = sgn(H)L magnitude of H nu/delta approximately +/- 1 with an amplitude at the minimum about 3.8 times the value at H = 0, the Casimir amplitude. For the normal transition the scaling function for fsolv has a single minimum near the continuation of the pseudocoexistence (capillary condensation) line, with an amplitude about 100 times the Casimir amplitude.