Static magnetic response of clusters in Co₀.₂Zn₀.₈Fe₁.₉₅Ho₀.₀₅O₄ spinel oxide

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Earlier investigation of Co₀.₂Zn₀.₈Fe₁.₉₅Ho₀.₀₅O₄ spinel has shown the existence of "super-ferromagnetic " clusters containing Fe³⁺ and Ho³⁺ ions along with small size clusters of Fe³⁺ ions (Bhowmik et al, J. Magn. Magn. Mater. 247, 83 (2002)). Here, We report the static magnetic response of these clusters. The experimental data suggests some interesting magnetic features, such as, enhancement of magnetization; re-entrant magnetic transitions with paramagnetic to ferromagnetic state below 225 K and ferromagnetic to spin glass state below 120 K; appearance of field induced ferromagnetism. We also observe an unusual maximum in the thermoremanent magnetization (TRM) vs temperature data. Our measurements suggest that this unusuality in TRM is related to the blocking of "super-ferromagnetic" clusters,out of the ferromagnetic state, along their local anisotropy axis.