SPIN-GLASS BEHAVIOR OF THE SYSTEM COFE2-XGAXO4

X-Ray, transport, infrared, magnetic hysteresis, a.c. susceptibility and Mossbauer studies have been carried out for the system CoFe2O4-CoGa2O4. X-Ray and transport measurements indicate cubic symmetry and p-type semiconductivity, respectively, for the compositions with 0.0 less-than-or-equal-to x less-than-or-equal-to 2.0. Hysteresis studies demonstrated the presence of ferrimagnetism in compositions with x less-than-or-equal-to 1.5, while the compound CoGa2O4 (x=2.0) showed antiferromagnetic behaviour. A.c. susceptibility (chi(ac)) measurements indicate that the compositions with x=0.25 and 0.50 undergo ferrimagnetic transitions at T(N) and on further cooling enter a cluster spin-glass state (T(sg)) with the magnetisation of different clusters being randomly frozen. The Mossbauer spectrum at room temperature for the composition with x=1.0 showed a relaxation pattern, while at 77 K a magnetically split six-line hyperfine spectrum coexists with a paramagnetic line at the centre.