gfactor of the21+state ofHf172

The $g$ factor of the ${2}_{1}^{+}$ state of $^{172}\mathrm{Hf}$ was measured using the perturbed angular correlation technique in a static external magnetic field. The result, $g({2}_{1}^{+})=0.25(5)$, is discussed in relation to the systematics of the previously reported $g$ factors in the Hf isotopes and compared with the predictions of several models. An interesting outcome of the analysis presented in this paper is the agreement between the calculated $g$ factors within the interacting boson approximation (IBA) and the results of a large-scale shell model calculation. This agreement supports the emphasis in the IBA on the valence space. The undershooting of the empirical $g$ factors near midshell in both models suggests that they underestimate the role of the saturation of collectivity, which is explicitly incorporated into a phenomenological model that agrees better with the data.