Magnetic dipole strength functions in heavy deformed nuclei

The isovector spin-flip M1 strength function in the deformed heavy nuclei $^{156}\mathrm{Gd}$ and $^{238}\mathrm{U}$ is calculated in the quasiparticle random-phase approximation. Interaction parameters are adjusted to reproduce the energies of isobaric-analog and Gamow-Teller excitations observed in (p,n) charge-exchange reactions. A phenomenological spreading width for decay into background 2p2h states is introduced and adjusted to reproduce the M1 spin-flip strength function recently observed by elastic scattering of tagged photons on $^{90}\mathrm{Zr}$ and $^{208}\mathrm{Pb}$. With the model parameters fixed in this fashion, our calculations predict large quantities of spin-flip M1 strength (10\char21{}20 ${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}^{2}$) between 5 and 10 MeV excitation in $^{156}\mathrm{Gd}$ and $^{238}\mathrm{U}$; it is strongly fragmented and should be observable by tagged-photon elastic scattering and proton inelastic scattering but probably not in high resolution inelastic electron scattering.