Coexistence of spin glass behavior and long-range ferrimagnetic ordering in La- and Dy-doped Co ferrite

• Published in: Journal of applied physics 2011-04, Vol.109 (7), p.07A510-07A510-3
• Main Authors: Bharathi, K. Kamala, Tackett, R. J., Botez, C. E., Ramana, C. V.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3562201

The structure, dc magnetization and ac susceptibility characteristics of the rare-earth (R=La,Dy) ionsubstituted cobalt-ferrites (CoO.Fe 1.925 La 0.075 O 3 and CoO.Fe 1.925 Dy 0.075 O 3 ) are evaluated. R-substituted Co-ferrites crystallize in the cubic inverse spinel phase. The irreversible temperature ( T irr ) between zero field cooled (ZFC) and field cooled (FC) magnetization for CoO.Fe 1.925 La 0.075 O 3 and CoO.Fe 1.925 Dy 0.075 O 3 determined from the temperature variation of magnetization measurements are 283 and 292 K, respectively. The broadening of ZFC magnetization and more than one maximum indicates the coexistence of short-range ferrimagnetic clusters of different size with a long-range ferrimagnetic phase. Magnetization curves indicate no saturation up to 30 kOe suggesting the canted spin structure inside the clusters. The relaxation times of spin clusters calculated using theVogel−Fulcher law for the frequency-dependent ac susceptibility measurements are on the order of ∼10 −6 s.