Magnetic excitations in the spin-glass phase of La2−xSrxCuO4

Abstract Magnetic excitations of La 1.95 Sr 0.05 CuO 4 were investigated using pulsed neutron inelastic scattering over a wide range of energy up to 300 meV. In contrast to the optimally doped superconductor the dynamical magnetic susceptibility χ ″ ( ω ) around ( π , π ) in the spin-glass phase monotonically decreases with increasing ω and nearly saturates beyond ∼50 meV. We found that the energy dependence of the q -position in the latter energy region is ascribed to a two-dimensional spin-wave dispersion relation with the nearest neighbor interaction J of 108±6 meV, which is smaller by ∼20% than that of La 2 CuO 4 .