Cluster glass behaviour in Co 0.2Zn 0.8Fe 2− xRh xO 4( x=0–1.0)

Abstract

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 Zn 2+ and B site is consequently diluted by non-magnetic Rh 3+ substitution in place of Fe 3+. The Rh substitution reduces antiferromagnetic exchange interaction between B site Fe 3+ ions and destroys the ferrimagnetic nature of the Co 0.2Zn 0.8Fe 2O 4 system. On diluting the B site moments, the system shows a typical cluster freezing phenomena at T⩽ 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.