Impact of Ho3+ Substitution on Structural, Morphological, Optical, Electrical, Thermoelectrical and Magnetic Properties of MgCuHoxFe2-xO4 (0 < x < 0.030) System

A series of rare earth (Ho3+) doped magnesium-copper nanoferrites with the general chemical compositions of Mg0.5Cu0.5HoxFe2-xO4 (where x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025 and 0.030) was fabricated by citrate sol-gel auto-combustion technique. The fabricated materials were investigated through powder XRD, FESEM, EDX, HRTEM, FTIR, UV-Vis, DC resistivity, TEP and VSM for magnetic properties. The crystallite size of the samples was determined to be in the range of 33-40 nm with increased Ho3+ content and the powder-XRD investigations validated the spinel cubic structure of the samples with the space group Fd3m. The analysis demonstrated that the lattice constant was reduced from 8.403 to 8.356 Å and according to the FE-SEM micrographs, the morphology of the samples were found to be spherical. The HR-TEM micrographs show that average particle size decreases from 64 to 48 nm. The FTIR examination revealed that their ν1 and ν2 absorption bands were located between 412-401 cm–1 and 562-547 cm–1, respectively and the optical band gap was found to be 2.77-3.28 eV. In Mg-Cu nanoferrites with Ho doping, there was no obvious increase in the elasticity moduli. It was observed that the thermal energy required to transform the p-type Mg-Cu nanoferrites from semiconducting to n-type semiconducting behaviour increases with increasing Ho doping and composition. The M-H loop saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) values were all enhanced when the Ho3+ concentration increased and varied anisotropically with Ho doping. The findings of this study suggested that Mg-Cu ferrites doped with Ho3+ might be beneficial for magnetic resonance imaging in biomedicine.