Effective critical exponents of magnetization in transverse Ising thin films

The characteristic influence of exchange interaction and transverse field at the surface on the critical behavior of a ferromagnetic transverse Ising thin film is examined by the use of the standard mean-field theory and the effective-field theory with correlations. The exchange interaction and transverse field at the surface take values different from those in the bulk. Depending on the ratios of these properties between the surface and the bulk, many characteristic behaviors are obtained in the magnetic properties, as discussed in the previous works (Physica A 319 (2003) 355; J. Magn. Magn. Mater. 264 (2003) 30; Phys. Stat. Sol. (B) 237 (2003) 592; Physica A (2003), published online). In particular, the critical effective exponent βeff of magnetization in the film with a thickness L is studied by the use of the two theoretical frameworks. We find some new phenomena of βeff, depending on the values of L and the ratios.