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

We have calculated the flux lattice melting curve and magnetization of YBa2Cu3O7-delta in the lowest Landau level approximation, using a Mon te Carlo technique which includes fluctuations in both the order param eter and the magnetic induction. There is a single first-order melting transition, at which long-range spatial order in the ab plane and the c direction disappear simultaneously, in agreement with recent measur ements of D. Lopez et al. The melting entropy is calculated to be abou t 0.034k(B) at a field of 5 T. The second temperature derivative of th e magnetization is positive in the solid phase and negative in the liq uid, in good agreement with experiment.