Anomaly in cluster glass behaviour of Co0.2Zn0.8Fe2O4 spinel oxide

We report cluster glass behaviour mixed with short-range ferrimagnetic ordering in Co0.2Zn0.8Fe2O4 spinel oxide. The AC susceptibility data show a maximum at T-f1 approximate to 110 K and a shoulder at T-f2 approximate to 212 K. The DC magnetization data also show a maximum at T-m1 approximate to 110 K and a shoulder at T-m2 approximate to 260 K. The frequency dependence of AC susceptibility and field dependence of DC magnetization data suggest a cluster spin-glass freezing at T-f1 approximate to 110 K. The appearance of shoulder in AC susceptibility data at T-f2 approximate to 212 K can be explained in terms of freezing of larger size clusters associated with anisotropy distribution. This is a pseudo-phase transition related to cluster size effect, rather than spin-glass-like freezing. The AC susceptibility, DC magnetization and room temperature Mossbauer spectroscopy measurements suggest that above 260 K the magnetic phase is dominated by short-range interacting clusters in paramagnetic state, called cluster-paramagnetie phase and at 110 K < T less than or equal to 260 K short-range ferrimagnetic phase coexist with cluster spinglass phase, called mixed magnetic phase, in the present system. (C) 2002 Elsevier Science B.V. All rights reserved.