g-boson panacea for magnetic properties of the nuclear groundstate band?
The magnetic moments of excited members of the groundstate band of even-even medium-mass nuclei are considered within the framework of the sdg-version of IBM-2. A novel asymptotic realisation of the variation-after-(angular-momentum)-projection Hartree-Bose approximation is employed. The introduction of an explicit g-boson degree of freedom is found not to resolve the discrepancy between the values of the d-boson g-factors required phenomenologically and those expected microscopically. Further study of the microscopic underpinning of the g-boson and improved experimental data are required to clarify matters: a promising testing ground would appear to be the Hf-Pt nuclei. Neither the present asymptotic realisation nor its predecessor (the "1/N-scheme") are appropriate when strong variations of magnetic moments within a groundstate band are encountered.