Study of the modified magnetic, dielectric, ferroelectric and optical properties in Ni substituted GdFe1-x Ni (x) O-3 orthoferrites

Polycrystalline GdFe1-x Ni (x) O-3 (x = 0.00, 0.02, 0.04) samples was synthesised using a glycine assisted sol-gel method to investigate the enhanced magnetic and electric properties of Ni substituted GdFeO3 systems. TG-DSC analysis of prepared samples confirms that GdFe1-x Ni (x) O-3 have good thermal stability in high temperatures. The system has been stabilized in an orthorhombic structure with space group Pbnm. The elemental composition of GdFe1-x Ni (x) O-3 has been estimated from EDAX spectrum. The results showed oxygen deficiency on increasing the Ni substitution and it has been supported by Rietveld refinement. FE-SEM images and Brunauer-Emmett-Teller analysis reveals that GdFe1-x Ni (x) O-3 is a highly porous material and its porosity and specific area increases with Ni substitution. Magnetic measurements indicates that the system exhibited ferrimagnetic behaviour at low temperatures and canted antiferromagnetic behaviour at room temperature. For x = 0.04 Ni content, magnetization reversal for applied field of 25 Oe has been observed. Increased coercivity of GdFeO3 with Ni substitution has been attributed to the grain size effect. From electrical point of view, dielectric permittivity of GdFeO3 has been enhanced with Ni substitution. This enhancement has been attributed to the cumulative effects of hopping of Fe2+-Fe3+ ions, grain-grain boundary contribution, and space charge polarization. The role of grain-grain boundary contribution is evident from electric modulus spectrum. The space charge effect has been realized in both impedance spectrum and dielectric loss. Temperature-dependent dielectric studies were conducted to understand the mechanisms and various aspects that contribute to the dielectric enhancement. A highly lossy capacitive nature in the P-E loop also suggests space charge effects due to Ni substitution in Fe sites. Availability of free charge carrier concentration is correlated with the optical properties of GdFe1-x Ni (x) O-3. The decrease of optical band gap (2.5-2.21 eV) on increasing Ni content suggests the increasing electronic contribution in the system.