Magnetic properties of crystallized iron phosphate glasses and relationship between structural and magnetic properties modifications that occur during crystallization have been investigated. Iron phosphate glass exhibits the spin-glass (SG) behavior and represents a prototype of solid with disordered spatially distributed magnetic moments. Glass of the composition 43Fe(2)O(3)-57P(2)O(5) (wt%) was heat-treated in air at 893, 923, and 1073 K for 24 h. The samples were studied using X-ray diffraction, Raman spectroscopy, and dc magnetic measurements. The magnetic measurements show dominant antiferromagnetic (AF) interactions for all samples. The starting glass exhibits SG behavior, whereas magnetic behavior of samples heat-treated at 893 and 923 K, which contain Fe-3(P2O7)(2) crystalline phase embedded in glass matrix, is ascribed to a mixture of super-paramagnetism and SG behavior. In the sample heat-treated at 1073 K, several peaks in the magnetization curves were observed which correspond to the various crystalline phases present in the sample: Fe-3(P2O7)(2), Fe-4(P2O7)(3) and Fe(PO3)(3). Hysteresis loops show paramagnetic behavior at 300 K. Small curvature is present at low temperature (5 K) that can be ascribed to the AF ordering in the samples.