Critical Behavior of Layered Superconducting Films in Parallel Magnetic Field

The equilibrium magnetization for layered superconducting films that experience a nonzero component, $H_{\parallel}$, of magnetic field applied parallel to the layers is computed at temperatures and at perpendicular field components in the vicinity of the decoupling transition. A fermion analogy is exploited for this purpose, whereby it is found that the parallel magnetization shows an anomalous $H_{\parallel}^{-1}$ tail at high fields due to entropic fluctuations of the (parallel) lattice of Josephson vortices. A collective pinning effect is also identified for $c$-axis transport limited by a single planar defect oriented parallel to both $c$ and to the applied magnetic field.