Investigating the lattice strains modified dielectric-optical properties and magnetic anisotropy of nanocrystalline Pr3+ substituted cobalt ferrite

Praseodymium-substituted CoPr x Fe 2-x O 4 nanoferrites (x = 0.0 - 0.3) were synthesized at 850 °C using a sol-gel method. XRD confirmed the cubic crystal structure and revealed notable changes in crystallite size (34 to 47 nm), lattice constant, and micro-strain as Pr 3+ content increased, indicating lattice distortion. FESEM analysis showed that grain size declined (from 266 to 118 nm) with increased Pr 3+ substitution at Fe 3+ lattice sites. The FESEM images also displayed prominent grain boundaries and a porous structure. HRTEM results indicated that particle size decreased from 50 to 46 nm with higher Pr 3+ concentrations. FTIR spectroscopy confirmed the formation of spinel ferrite via the identification of metal oxide bonds. Room-temperature photoluminescence spectra (from 419 to 595 nm) revealed crystallographic defects, near-band emissions, and oxygen deficiencies. With increased Pr 3+ , saturation magnetization, coercivity, and magnetic anisotropy also changed notably. Saturation magnetization, squareness ratio, and magnetocrystalline anisotropy constant increased as x rose from 0 to 0.2. The substituted ferrites showed enhanced coercivity (1047 to 1322 Oe) compared to pristine cobalt ferrite (1016 Oe). The dielectric constant increased systematically with added Pr 3+ , while dielectric loss declined substantially, indicating suitability for high-frequency device applications. Improved magnetic parameters and crystallographic defects with porosity may make these materials useful in permanent magnets and hydroelectric cells.