Strong correlation between Dy3+ concentration, structure, magnetic and microwave properties of the [Ni0.5Co0.5](DyxFe2-x)O4 nanosized ferrites.

The dysprosium ions (Dy³⁺)-substituted nanosized ferrites (NFs) of composition [Ni 0.5 Co 0.5 (Dy x Fe 2-x)O 4 (x ≤0.08) were prepared using the citrate gel process. To analyse the magnetic properties of the samples, the Mössbauer spectroscopy methods and vibrating sample magnetometry (VSM) were applied. The room temperature Mössbauer spectra were fitted to determine the hyperfine parameters of the proposed NFs. The preferential occupation of the octahedral B sites by the Dy³⁺ in the spinel ferrite sublattice was confirmed from the cations distribution. The hyperfine magnetic field of both sublattice decreased whereas the increase in the Dy³⁺ substitution was observed. The S-parameters of the prepared NFs in the high frequency range were measured by the co-axial method. In addition, the MW reflection losses were evaluated by means of the frequency-dependent (in the range of 1–20 GHz) complex permittivity and permeability spectra. All the NFs indicated that the absorption of the electromagnetic radiation was ranging between 2.9–5.5 GHz due to the natural ferromagnetic resonance. A correlation amongst the Dy³⁺ concentration, microstructure, magnetic and microwave (MW) characteristics of these NFs was established. It's been asserted that by controlling the Dy³⁺ contents carefully, the MW absorption and magnetic attributes of the proposed spinel NFs can be tailored. [ABSTRACT FROM AUTHOR]