Spin–glass behaviour of the system CoFe2–xGaxO4
Abstract
X-Ray, transport, infrared, magnetic hysteresis, a.c. susceptibility and Mössbauer 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⩽x⩽2.0. Hysteresis studies demonstrated the presence of ferrimagnetism in compositions with x⩽1.5, while the compound CoGa2O4(x= 2.0) showed antiferromagnetic behaviour. A.c. susceptibility (χac) measurements indicate that the compositions with X= 0.25 and 0.50 undergo ferrimagnetic transitions at TN and on further cooling enter a cluster spin–glass state (Tsg) with the magnetisation of different clusters being randomly frozen. The Mössbauer 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.