Magnetization process in cluster spin glass model in the low temperature region

An ensemble of magnetic clusters is approximated by an ensemble of two-singlet systems: at each lattice site l there are two levels, ?_l,1 and ?_l,2. ?_l,1 is associated with spin zero and ?_l,2 with spin 1 (or vice versa). Δ = ?_l,2??_l,1 originates from some intra-cluster interaction and some effective magnetic field; for the both some distribution is assumed. An exchange interaction between different clusters is also taken into account. The excitation spectrum of this ensemble as function of H_ext is calculated and applied to discuss the response of the system to some external magnetic field H_ext in the low-temperature region. Typical instabilities of magnetization as function of H_ext are obtained. Finally, possible applications of our results to spin-glass systems are discussed.