FIRST-ORDER VORTEX LATTICE MELTING AND MAGNETIZATION OF YBA2CU3O7-DELTA

We present the first non-mean-field calculation of the magnetization M(T) of YBa2Cu3O7-delta both above and below the flux-lattice melting temperature T-m(H), in good agreement with experiment. Fluctuations in both order parameter psi(r) and magnetic induction B are included in the Ginzburg-Landau free energy. The second derivative (partial derivative(2)M/partial derivative T-2)(H) is predicted to be negative throughout the vortex liquid state and positive in the solid state. The discontinuity in entropy at melting is calculated to be similar to 0.034k(B) per flux Line per layer at 50 kOe.