Structural and paramagnetic resonance properties correlation in lanthanum ion doped nickel ferrite nanoparticles

Abstract

La3+ ion doped in nickel nanoferrite with different compositions were prepared by sol-gel route and characterized by different techniques. La3+ions substitution induces dislocation and deformity in lattice to soften the lattice. XRD patterns confirmed the polycrystalline nature of nanoparticles with no extra phase as per JCPDS card no. 071–1232 with increase in lattice constants on substitution of larger ionic radii La3+ions at Fe3+sites. ν1Fe-O stretched vibrations of A- (Tetrahedral) and ν2Fe-O of B- (Octahedral) complexes are observed at 598 cm−1and 419 cm−1respectively in IR transmission graphs. The broadening of both stretching vibrational modes with La3+ion content is attributed to the reduction in grain size arising from the lattice distortion by cation distribution, interactions among nanoparticles and La3+ion concentration. On increasing La3+ion concentration, the variations in the intensity of ν1band are more pronounced as compared to ν2band which confirms the preferred substitution of La3+ion at octahedral site by expanding the B-site radii. FESEM micrographs exhibit the homogeneous and agglomerated nanoparticles pattern of these doped analogues. EPR spectra exhibit broad ferromagnetic signal with no characteristic peak of SPM feature. The peak to peak line width and g-value increases on increasing La3+ion concentration in samples. These morphological and magnetic properties can be exploited for their use in the development of stable ferrofluid for heat sink application and as sensing electrode in chemical/bio sensors.