Cluster glass behaviour in Co0.2Zn0.8Fe2-xRhxO4(x=0-1-0)

We report the low field magnetic behaviour of Zn- and Rh-substituted Co ferrite by AC susceptibility, DC magnetization, hysteresis measurement and relaxation experiment, The present system is a cubic spinel, where 80% of A site is diluted by non-magnetic Zn2+ and B site is consequently diluted by non-magnetic Rh3+ substitution in place of Fe3+. The Rh substitution reduces antiferromagnetic exchange interaction between B site Fe3+ ions and destroys the ferrimagnetic nature of the Co0.2Zn0.8Fe2O4 system. On diluting the B site moments, the system shows a typical cluster freezing phenomena at T less than or equal to T-f due to frustration effect. We propose a zero field cooled relaxation technique that can easily identify the mixture of small frustrated clusters or spins along with the strongly coupled clusters. It has been observed from the field dependence of DC magnetization that for x = 1.0, there is a crossover from de Almeida-Thouless (AT)-like line to Gabay-Toulouse (GT)-like line at the freezing temperature, (C) 2001 Elsevier Science B.V. All rights reserved.