Influence of substrate induced strain on B-site ordering and magnetic properties of Nd₂NiMnO₆ epitaxial thin films

Epitaxial thin films of double perovskite Nd₂NiMnO₆ (NNMO) have been successfully grown on (001) oriented substrates of (LaAlO₃)_0.3-(Sr₂AlTaO₆)_0.7 (LSAT), SrTiO₃ (STO) and LaAlO₃ (LAO) by pulsed laser deposition under optimum growth conditions. X-Ray diffraction and reciprocal space maps of the asymmetric (103) peak reveal that the films deposited on LSAT and STO substrates are fully relaxed, while a large in- plane compressive strain has been observed in film grown on LAO. This results into the coexistence of anti-site disorder and orthorhombic phase in the film deposited on LAO, which is further confirmed from observed shift and broadening in the antisymmetric vibrations in the Raman spectra. The temperature dependent magnetization shows a ferromagnetic transition close to 200 K in all the three samples. However, film grown on LAO substrate shows an additional upturn transition at ~ 96 K (T′), which could be ascribed to the formation of antisite disorders further responsible for reduction of saturation magnetization (~ 1.8 × 10⁵ A/m) in hysteresis curve of the sample. The ordered structure obtained on LSAT and STO exhibit in-plane easy axis with a large coercivity of ~ 0.2 T, while, the film deposited on LAO does not show any preferred anisotropic direction. - Highlights: • Epitaxial Nd₂NiMnO₆ thin films were deposited by pulsed laser deposition. • Reciprocal space maps reveal the strained or relaxed state of thin films. • B-site ordering or disordering in the films was confirmed by Raman spectroscopy. • All the films show a ferromagnetic transition close to 200 K. • Magnetic hysteresis loops suggest the magnetic anisotropic direction.