MAGNETIC AND THERMAL-PROPERTIES AT THE IN ITIAL-STAGE OF FORMATION OFSPIN-GLASS TYPE STATES IN LI0.5FE2.5-XGAXO4 (X=0.9, 1,0) SYSTEM

It is found from complex studies of the thermal and magnetic propertie s on polycrystal samples of diluted ferrimagnetic spinels Li0.5Fe2.5-x GaxO4 containing nonmagnetic Ga3+ ions (x = 0.9, 1.0) that at the init ial concentrations of the formation of disordered spin glass (SG) type states, when the nonzero spontaneous magnetization of the longitudina l spin components coexists with the longrange SG order for the transve rse components, the low-energy excitations are spin waves obeying the quadratic dispersion law. They destroy the long range SG order in T(f) . The presence of noncorrelated disorder at T > T(f) leads, in additio n to the spin waves, to modes of some other nature, which shows up as maxima in the dependence C(m)(T).