Low-energy M1 strength from shell-model calculations

Large-scale shell-model calculations were performed for 56Fe, 60Fe, 64Fe, 68Fe. The collective properties of yrast states are reproduced in the used model space.
The low-energy enhancement of M1 strength decreases with increasing neutron number while a bump around E = 3 MeV develops, which can be related with the scissors mode. The strength around E = 3 MeV includes transitions from 1+ states to the ground state as well as to excited 0+ states and contributions from other spins. This may explain the higher strength found in ion-induced reactions compared with the one observed in photon scattering.