DIRECT OBSERVATION OF A MAGNETIC GAP IN SUPERCONDUCTING LA1.85SR0.15CUO4 (T-C=37.3 K)

Neutron inelastic scattering experiments have been performed on homogeneous single crystals of La1.85Sr(0.15)CuO(4) with T-c = 37.3 K (at onset), higher than any previously studied single crystals. The temperature dependence of the low energy incommensurate peak intensity at (pi(1 +/- delta), pi) and (pi, pi(1 +/- delta)) exhibits a pronounced maximum near T-c. In contrast to the results reported on lower T-c crystals, the intensity below 3.5 meV dramatically decreases as the temperature decreases below T-c, vanishing into the background below similar to 15 K. The behavior is consistent with predictions based on a d(x2-y2) superconducting order parameter.