Investigation of structural and magnetic properties of Ni0.5Zn0.5Fe2O4 nano powders prepared by self combustion method

Graphical abstract: Display Omitted Highlights: ► Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} prepared by self combustion with uniform/nonuniform heating. ► Characterized using TEM, XRD, in-field Mossbauer and DC magnetometry. ► Leads to bimodal (S1) and very narrow size distribution (S2) type nano samples. ► S1 has magnetic properties of bulk Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}. ► Although very even sized, S2 large magnetic anisotropy distribution. -- Abstract: Nano powders of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} have been synthesized by the self-combustion method at a relatively low temperature of 473 K under conditions of non-uniform and uniform heating. Rietveld fitting of X-ray diffractograms confirm the formation of the pure spinel phase in both samples. Transmission electron microscopy indicates that the sample prepared under non-uniform heating has a bimodal particle size distribution (average values 16 nm and 6 nm) while the one prepared under uniform heating has a very narrow particle size distribution (average size 4 nm). Low temperature, in-field Mossbauer spectroscopic studies clearly show surface spin contributions. The hyperfine fields and Curie temperature of the non-uniformly heated sample are in good agreement with those reported for the corresponding bulk samples. Despite having a very narrow particle size distribution, the uniformly heated samplemore » has a large anisotropy distribution which is evident in the broad transition visible in the temperature dependent magnetization curve. It is also corroborated by the fact that the experimental magnetization curve at room temperature requires two Langevin functions for satisfactory reproduction.« less