B-site ordering effect on structural and magnetic properties of ‘Y’-modified double perovskite La2NiMnO6 nanoparticles

Abstract

Rietveld refinement profile of X-ray diffraction pattern confirms the pure-phase rhombohedral structure of La2NiMnO6 (LNMO) and ‘Y’-doped LNMO nanoparticles corresponding to the space group R$$\stackrel{-}{3}$$c (SG No.: 167) with the crystallite size lying in the range of 25–16 nm. The antiferromagnetic (AFM) to strong ferromagnetic (FM) transition has been observed through M–H hysteresis loops from room temperature to extremely low temperature (2 K) for LNMO and ‘Y’-doped LNMO nanoparticles. An extraordinary magnetic moment of 4.16 to 6.25 µB per formula unit was achieved after the doping of ‘Y’ (nominally 2 to 4%) into LNMO. The temperature-dependent magnetization studies confirm the transition temperature (~ 273 K) for LNMO and LNMO2 (LNMO-2%Y) nanoparticles due to the antisite defects beside the FM ordering of the Ni-Mn sites and lower transition temperature (~ 230 K) for LNMO4 due to the local structural distortion and the superexchange interaction in FM Ni2+($${t}_{2g}^{6}{e}_{g}^{2}$$) – O($$2p$$) – Mn4+($${t}_{2g}^{3}{e}_{g}^{0}$$).