Magnetic properties of nanostructured ferrimagnetic zinc ferrite

Abstract

Nanostructured ZnFe 2 O 4 ferrites with different grain sizes were prepared by high energy ball milling for various milling times. Both the average grain size and the root mean square strain were estimated from the x-ray diffraction line broadening. The lattice parameter initially decreases slightly with milling and it increases with further milling. The magnetization is found to increase as the grain size decreases and its large value is attributed to the cation inversion associated with grain size reduction. The 57 Fe Mössbauer spectra were recorded at 300 K and 77 K for the samples with grain sizes of 22 and 11 nm. There is no evidence for the presence of the Fe 2+ charge state. At 77 K the Mössbauer spectra consist of a magnetically ordered component along with a doublet due to the superparamagnetic behaviour of small crystalline grains with the superparamagnetic component decreasing with grain size reduction. At 4.2 K the sample with 11 nm grain size displays a magnetically blocked state as revealed by the Mössbauer spectrum. The Mössbauer spectrum of this sample recorded at 10 K in an external magnetic field of 6 T applied parallel to the direction of gamma rays clearly shows ferrimagnetic ordering of the sample. Also, the sample exhibits spin canting with a large canting angle, maybe due to a spin-glass-like surface layer or grain boundary anisotropies in the material.

Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory

“…33,70 Also, the isomer shift obtained for the paramagnetic doublet matches neither the tetrahedral nor the octahedral Fe 3+ isomer shift values in nanocrystalline ferrimagnetic zinc ferrites. 64,71 In the Fe-doped ZnO system, Fe ions are present in the tetrahedral site. If, due to the presence of the cation vacancy, the valence state changes to +3, the crystal field no longer possesses tetrahedral symmetry and hence the isomer shift may not match the value corresponding to tetrahedral sites.…”

Effect of thickness on magnetic and microwave properties of RF-sputtered Zn-ferrite thin films

“…The magnetic properties of ZnFe 2 O 4 films also show a strong dependence on the grain size. [1][2][3][4]8 Most of the studies carried out on these films in literature, however, vary the grain size either by changing the substrate temperature during deposition or through post deposition annealing. 9,10 In the present paper, we report a study of the magnetic properties on ZnFe 2 O 4 thin films with varying thickness (t).…”

INFLUENCE OF TIME AND TEMPERATURE ON RESISTIVITY AND MICROSTRUCTURE OF Cu_x Co_1-x Fe₂ O₄ MIXED FERRITES

“…are greatly influenced by porosity, grain size and microstructure of the sample [16,17]. Ferrites containing Cobalt and Copper exhibit several interesting properties which make them suitable for switching and memory devices.…”