Substrate orientation dependent characteristics of half-metallic and metallic superlattices [La0.7Sr0.3MnO3/LaNiO3]10

Abstract

We report a detailed study on the orientation dependent growth characteristics, electronic structure, transport, magnetic, and vibrational excitations in atomically flat interfaces of [Formula: see text] superlattices (SLs) coherently grown on (001/011/111)-[Formula: see text] substrates by the pulsed laser deposition technique. X-ray reflectometry confirms the periodic superlattice stacks from the Kiessig interference fringes and well-defined even interfaces between the nickelate and manganite layers. A complex local atomic environment across the interfaces was noticed, yet trivalent La, divalent Sr, and mixed valent Ni[Formula: see text] and Mn[Formula: see text] electronic states prevail at the core level with enhanced relative intensity ratio of the Mn ions in the superlattices grown on (111) oriented [Formula: see text] substrates as compared to those grown on (001) and (011) oriented [Formula: see text]. The temperature ([Formula: see text]) dependence of electrical resistivity [Formula: see text] analysis reveals 3D variable range hopping model [[Formula: see text]] with large magnitude of hopping energies ([Formula: see text]40 meV) for the SL-111 system associated with the high energy gap developed by the accumulation of disorderness in the individual constituents of polar layers. Moreover, all SL systems exhibit reduced ferromagnetic ordering temperatures ([Formula: see text]) with a low-temperature anomaly ([Formula: see text]) and a substantial enhancement in the effective exchange interaction ([Formula: see text]) having altered ground state-spin configuration [Formula: see text] different from [Formula: see text] of [Formula: see text]. Nevertheless, the SL-011 system exhibits large anisotropy field [Formula: see text] and cubic anisotropy constant [Formula: see text] in comparison to the other two orientations. The second order two-phonon interaction driven by the local polaronic distortion causes significant changes in the vibrational excitations of the investigated system. Nonetheless, most of the Raman modes follow the substrate-induced, highly oriented epitaxial growth pattern except for two modes [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]), which slightly differ in the case of SL-111 superlattices.