Magnetic dynamics and form factor in La2CuO4

Complete text of publication follows. The magnetic excitations in the insulating two-dimensional (2D) spin-1/2 antiferromagnet La2CuO4 have been measured throughout the Brillouin zone using high-resolution pulsed neutron scattering techniques. The dispersion relation has been compared with a spin-wave model for a 2D Heisenberg spin Hamiltonian. Improved estimates of the nearest-neighbour exchange J and next-nearest-neighbour coupling constant J' are given. The magnetic form factor f(Q) has been extracted by comparing the low-energy inelastic magnetic scattering observed at equivalent positions in the 2D magnetic zone and at different values of the total wavevector transfer Q, and the results are in good agreement with calculations of the magnetic form factor for a Cu2+ 3d hole with x2-y2 orbital symmetry in the Cu-O planes and are in disagreement with a spherical form factor for free Cu2+ ions. (author)