FORMATION OF LONG-RANGE FERRIMAGNETIC ORDER IN DILUTE SPINELS LI0.5FE2.5-XGAXO4 NEAR THE MULTICRITICAL POINT

The influence of spatial inhomogeneity of short-range exchange on the formation of long-range ferrimagnetic order in dilute spinels is inves tigated. The objects of investigation are two types of polycrystalline samples of Li0.5Fe1.1Ga1.4O4 differing in the extent of heterogeneity in the distribution of magnetic (Fe3+) and nonmagnetic (Ga3+) ions in the lattice. The heterogeneity was created by using two regimes of th ermal treatment, i.e., slow cooling (S) and quenching (Q) of samples f rom 1550 to 300 K. The results of analysis of magnetization isotherms sigma(T)(H) at T= 4.2 K, (77-300) K, H less than or equal to 16 kOe an d temperature dependences of initial susceptibility chi T(T) show that the long-range ferrimagnetic order near the multicritical point (x(0) 1.5) of the x-T phase diagram is stable to variations of the degree o f spatial heterogeneity of the exchange. (C) 1997 American Institute o f Physics.