Pair condensate in realistic shell model states. Part 2: M1 states in 54,56Cr and 56,58,60Fe

The possible microscopic realization of Interactive Boson Model (IBM) collective M1 modes is investigated for 54,56Cr and 56,58,60Fe, using a shell model space of protons in the 1f7/2 orbit and neutrons in the 2p3/2, and 2p2/2 orbits. Distributions of the pair-analogues of IBM-2 mixed-symmetry states, and of some g-IBM-2 states, over shell model eigenstates are explicitly determined. For J = 1, the mixed-symmetry SD strength is generally lower than that of the G-pair states, and responsible for most of the low-energy M1 strength. Structures incorporating extended sets of levels, including the M1 states, corresponding to the sd-IBM-2 dynamical symmetry representations are manifest in the shell model spectra for 56Fe and 54Cr. The correspondence with observed levels is discussed. 24 refs., 3 tabs., 2 figs