  The nature of the Griffiths phase in three-dimensional Ising random magnet
Ni_{p}Mg_{1-p}(OH)_{2} (p = 0.10, 0.25, 0.315, 0.50, 0.80, and 1) is studied
from the measurements of absorption (the out-of phase in AC magnetic
susceptibility) in the field-cooled (FC) state. The temperature (T) dependence
of absorption is measured in the vicinity of the critical temperature [N\'{e}el
temperature for p = 0.50, 0.80, 1, and the spin glass transition temperature
for p = 0.1, 0.25, 0.315] in the presence of an external magnetic field H. A
broad peak is clearly observed for absorption vs T well above the critical
temperature at H > 20 kOe. This result gives a piece of evidence for the
magnetic-field induced Griffiths phase.
