Superparamagnetic behaviour and evidence of weakening in super-exchange interactions with the substitution of Gd3+ ions in the Mg–Mn nanoferrite matrix

The Gd3+ substituted Mg–Mn nanoferrites with generic formula Mg0.9Mn0.1GdxFe2−xO4 (x = 0.05, 0.1, 0.2, 0.3) have been prepared for the first time by self-ignited solution combustion method. The X-ray analysis confirmed the formation of single phase cubic spinel structure. Gd3+ substitution has resulted in an increase in the crystallite size (13.4–16.1 nm) and lattice parameter (8.35–8.38 Å). The M–H and ZFC–FC study revealed that all nanoferrites are of superparamagnetic in nature. The saturation magnetization (Ms) has been observed to decrease with the incorporation of Gd3+ ions. The cation’s distribution has been estimated by using the magnetic characterization method. The magnetic properties such as initial permeability (μi) and magnetic loss tangent (tan δ) have been investigated as a function of frequency. The initial permeability has been observed to be almost constant with frequency and in each nanoferrite an onset of resonance is observed. In addition, very low values of ‘tan δ’ were obtained.