Effect of trivalent lanthanide substitution on novel Nd2FeMnO6 double perovskite compounds
Synthetic double perovskites are a group of oxide materials which plays a crucial role in the progress of solid state lasers, magnetic and optic-electronic devices. The search on solubility of rare-earth elements in the well-crystallized system shows the way to the discovery of unique oxide materials with multifunctional properties. By ensuing the above importance, the trivalentlanthanide substitution on Nd2FeMnO6 double perovskite compounds are synthesized using conventional solid-state reaction technique and the structural, electrical, optical and magnetic properties of the prepared compounds have been studied. The Rietveld refinement of powder X-ray diffraction patterns have been started with the structural model of NdFeO3 orthoferrite and found with excellent goodness of fit for the orthorhombic symmetry with Pbnm space group. Thus, it is confirmed that the substituted Mn–ion has become stable into double perovskite Nd2FeMnO6 crystal structure. The La-substituted samples exhibit trivial increase in lattice cell parameters and volume of the unit cell appropriate to the substitution of larger ionic radii La3+ion while comparing with Nd3+ ion. The X-ray photoelectron measurements make known the existence of Nd, La, Mn and Fe ions in +3 oxidation states and reveal the stable double perovskite structure. The La-substituted samples show no major variation in morphology while comparing with parent Nd2FeMnO6 compound. Raman spectral analysis confirmsthe presence of Nd2FeMnO6 phase, which are specified by the deviation from NdFeO3orthoferrite phase. The substitution of La3+ ions into the Nd2FeMnO6 double perovskite structure is also notified from the Raman analysis. The photoluminescence studies show that the samples can be excited by the blue and ultra-violet light radiation. The magnetization investigation reveals that the Nd2FeMnO6 sample exhibits super-paramagnetic ordering due to the presence of Fe, Mn and Nd ions in the lattice. It is also identified that the substitution of La3+ ion disturbs the locked-in spins in Nd2FeMnO6 system to exhibit better magnetic behaviour in the presence of external magnetic field. Hence from the present investigations, it is noted that the effect of trivalent lanthanide substitution on Nd2FeMnO6 compound leads to possible tailoring of multifunctional properties in the double perovskite system.
Keywords: Double Perovskites, Orthoferrites, Rietveld Refinement, Photoluminescence, Micro Raman, Super-paramagnetic ordering, UV – DRS, XPS