  B-T phase diagram and phase transitions of interlayer Josephson vortices are
investigated. For magnetic fields above a critical value, we find a
Kosterlitz-Thouless (KT) type intermediate phase characterized by in-plane
two-dimensional, quasi long-range orders (QLROs) of vortex alignment and
superconductivity. The transformation to high-temperature normal phase is a KT
transition. The evolution to low-temperature phase of three-dimensional (3D)
LRO of vortex alignment is a second-order phase transition in the 3D XY
universality class. For low magnetic fields, a single first-order melting
transition of the Josephson vortex lattice is observed. The present study
therefore indicates a multicritical point in the B-T phase diagram.
