Effect of bulk magnetic field on critical Ising films

Two-dimensional Ising films Lx infinity in a nonvanishing bulk magnetic field H are studied at the bulk critical temperature T-c for two choices of surface fields (a) H-1=H-L=0 (ordinary transition), and (b) H-1=H-L=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 to, and for the analog of the solvation force f(solv) are found and discussed. When H-1=0 the scaling function for f(solv) has two symmetric minima at y = sgn(H)L\H\ (v/Delta) approximate to +/- 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 f(solv) has a single minimum near the continuation of the pseudocoexistence (capillary condensation) line, with an amplitude about 100 times the Casimir amplitude.