Magnetic study on Co0.2Zn0.8Fe2-xGaxO4(x=0-1) spinel oxide

We report the magnetic study on a series of Ga substituted Co0.2Zn0.8Fe2-xGaxO4 spinel oxide. The cations distribution, obtained from Mossbauer spectra, suggest that conventional ferrimagnetic structure, i.e., the existence of magnetic moments on both A and B sites, is destroyed for x greater than or equal to 0.2 samples. We observe a non-monotonically increase of ferromagnetic correlations between the B site spins. The samples with x = 0.2-0.6 shows a mixture of perturbed ferromagnetism and cluster spin glass behaviour. The perturbed ferromagnetic phase of the samples has been explained in terms of B site spin canting. The increase in magnetic frustration and competition between exchange interactions stabilizes the x greater than or equal to 0.8 samples in a cluster spin glass like state. The field cooled thermoremanent magnetization measurement for x = 0.4 sample suggest that the cluster nucleation process is not only thermally activated but also strongly depends on the temperature (T-a), where field has been applied during cooling process of the sample. (C) 2002 Elsevier Science B.V. All rights reserved.