Observation of a magnetic-field-induced Griffiths phase in three-dimensional Ising random magnet Ni_(p)Mg_(1-p)(OH)₂ from absorption of AC magnetic susceptibility

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.