Synergy-induced enhancement of magnetic properties in α -Fe 2 O 3 /Ni 1+ x Fe 2- x O 4 nanocomposites: role of Ni 2+ and annealing temperature

The effect of thermal annealing on the structural, optical and magnetic properties of α -Fe 2 O 3 /Ni 1+ x Fe 2- x O 4 ( x = 0.05 and 0.10) nanocomposites was probed through different characterization techniques. The structural study revealed the formation of nanocomposite samples because of the co-existence of both α -Fe 2 O 3 and NiFe 2 O 4 phases. The NiFe 2 O 4 phase in the nanocomposite increased with the increase of both Ni 2+ and annealing temperatures. The morphological study reveals the presence of agglomerated irregular elliptical particles. The optical band gap of the samples remains unchanged with the increase of Ni 2+ and annealing temperature. All the synthesized samples display effective exchange coupling and ferromagnetic features at room temperature. The magnetization of these systems increases with increasing NiFe 2 O 4 phase and the progressive increase in magnetization is observed for the nanocomposites annealed at higher temperatures. The magnetization study at different temperatures revealed that there exists a critical measuring temperature for individual samples beyond which the magnetization starts reducing. The exchange bias in the nanocomposite samples depends on effective coupling between α -Fe 2 O 3 and NiFe 2 O 4 phases and the same is higher for the samples with x = 0.05.