Universal magnetic excitation spectrum in cuprates

Wehave recently used inelastic neutron scattering to measure themagnetic excitation spectrum of La1.875Ba0.125CuO4 up to 200 meV. This particular cuprate is of interest because it exhibits static charge and spin stripe order. The observed spectrum is remarkably similar to that found in superconducting YBa2Cu3O6+x and La2−xSrxCuO4; the main differences are associated with the spin gap. We suggest that essentially all observed features of the magnetic scattering from cuprate superconductors can be described by a universal magnetic excitation spectrum multiplied by a spin gap function with a material-dependent spin-gap energy.