The dependence of magnetic moment and susceptibility on temperature, magnetic field and frequency of some single crystals Mn_1−xZn_xF₂ (x≈x_e=0.75—percolation limit) were experimentally investigated. Our experiments show that (Bazhan and Petrov 1984; Cowleyet al 1984; Villain 1984) in these crystals the nonequilibrium magnetic state of spinglass type with finite correlation length appears as temperature decreasesT<T in weak magnetic fields. This state is determined by fluctuation magnetic moments √nμ (wheren is the number of magnetic ions, corresponding to finite correlation length andμ the magnetic moment Mn⁺¹).

In the experiments in low magnetic fields and frequencies there are no peculiarities in the magnetic susceptibility temperature dependence atT≠T_f. At temperaturesT>T_f andT<T_f magnetic susceptibility is determined by$$\chi \left( {T > T_f } \right) = \frac{{N\left\langle \mu \right\rangle ^2 }}{{3k\left( {T + \theta } \right)}} = \frac{N}{n}\frac{{\left\langle {\sqrt n \mu } \right\rangle ^2 }}{{3k\left( {T + \theta } \right)}} = \chi \left( {T< T_f } \right)$$. In strong magnetic fields and large frequencies there are peculiarities in thex(T) dependence atT=T_f. AtT<T_f and strong magnetic fieldsX(T)=x₀ andT<T_f and at large frequenciesx(T)=x₀+α/T.

The dependences of magnetic susceptibility on the frequency are determined by the magnetic system relaxation. Calculations and comparison with experiments show that the relaxation of the investigated magnetic systems atT<T_f follows the relaxation lawM(t)=M(0) exp[−(t/τ)^r], suggested in Palmeret al (1984) for spin-glasses relaxation taking into account the time relaxation distributionτ₀....τ_max in the system and its ‘hierarchically’ dynamics.