Hyperfine Anomaly of Be Isotopes and Anomalous Large Anomaly in ¹¹Be

A new result of investigations of the hyperfine structure (hfs) anomaly in Be isotopes is presented. The hfs constant for $^{11}$Be is obtained by using the core plus neutron type wave function: $ |2s_{1\over 2}>+|1d_{5\over2}\times 2^+ ; {1/2}^{+}> $. A large hfs anomaly of $^{11}$Be is found, which is mainly due to a large radius of the halo single particle state.