The magnetic moment of ${}^{11}\mathrm{Be}$ ( $T_{1/2}=13.8\mathrm{s}$) was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a ${}^{11}{\mathrm{Be}}^{+}$ ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal, and observation of rf resonances in the asymmetric angular distribution of the $\beta$ decay ( $\beta$-NMR). The nuclear magnetic moment $\mu {(}^{11}\mathrm{Be})=-1.6816\mathrm{}(8){\mu }_N$ provides a stringent test for theoretical models describing the structure of the $1/2^{+}$ neutron halo state.

• Received 26 May 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.3792