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 t emperature T-m(H), in good agreement with experiment. Fluctuations in both order parameter psi(r) and magnetic induction B are included in t he Ginzburg-Landau free energy. The second derivative (partial derivat ive(2)M/partial derivative T-2)(H) is predicted to be negative through out the vortex liquid state and positive in the solid state. The disco ntinuity in entropy at melting is calculated to be similar to 0.034k(B ) per flux Line per layer at 50 kOe.