Tuning of composite cubic spinel structure in Co1.75Fe1.25O4 spinel oxide by thermal treatment and its effects on modifying the ferrimagnetic properties

• Published in: Journal of alloys and compounds 2016-09, Vol.680, p.315-327
• Main Authors: Bhowmik, R.N., Kazhugasalamoorthy, S., Ranganathan, R., Sinha, A.K.
• Format: Article
• Language: English
• Subjects: Co rich ferrite; Exchange bias; Ferrimagnet; Magnetic blocking; Multi-phased spinel
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.04.163

We have synthesized the Co1.75Fe1.25O4 spinel ferrite by chemical reaction of Co and Fe nitrates at alkaline medium. We have annealed the as-prepared material up to 1100 °C to study the changes in lattice structure and magnetic properties. We have used synchrotron X-ray diffraction and Raman spectroscopy to identify the lattice structure. The material formed a composite spinel structure of Co rich phase (20–30%) and Fe rich phase (80–70%) for annealing temperature range 200–800 °C, and single phased spinel structure at 900 °C. At annealing temperature 1100 °C, the sample showed minor amount of hematite phase, in addition to two spinel phases. All the samples are ferrimagnetic in nature, but ferrimagnetic properties in mixed-phased samples are distinctly different from single phased sample. The analysis of the temperature and magnetic field dependence of magnetization data revealed a wide distribution of exchange interactions, anisotropy barriers, blocking of magnetic domains, and exchange bias for the samples having multi-phase components. On the other hand, single phased sample has shown the highest magnetization and the smallest coercivity with lowest distribution of magnetic exchange energy and anisotropy. (a) Room temperature SXRD pattern fitted with Fullprof program for samples of Co1.75Fe1.25O4 composition and (b) shows the SXRD pattern about (311) peak. The lattice parameters, spinel phase components and grain size are shown as insets. [Display omitted] •We prepared spinel oxide Co1.75Fe1.25O4 in single phased and multi-phased form.•Ferrimagnetic properties depend on thermal activated structural phase change.•The single phased sample showed soft ferrimagnetic character.•The multi-phased samples showed hard ferrimagnetic character.