Magnetic hyperfine field distributions in ferrimagnetic spinels Fesub(2(1-y))Mgsub(1+y)Tisub(y)Osub(4) with y<=0.5

Moessbauer effect measurements at temperatures above 77K have been performed on a number of Fe-rich samples with general formula Fesub(2(1-y))Mgsub(1+y)Tisub(y)Osub(4) with y<=0.5. It is found that the magnetic hyperfine structure is strongly influenced by the number of diamagnetic ions present in the lattice. Even for rather low diamagnetic substitution rate (y=0.2, 0.3), relaxation effects are observed at temperatures far below the corresponding Neel temperatures. For higher values of y, the spectra show the simultaneous presence of a strongly broadened or relaxed six-lines pattern and a quadrupole doublet. The origin of the observed properties is discussed