Creating Ferromagnetic Insulating La_0.9Ba_0.1MnO₃ Thin Films by Tuning Lateral Coherence Length

Abstract

In this work, heteroepitaxial vertically aligned nanocomposite (VAN) La 0.9 Ba 0.1 MnO 3 (LBMO)-CeO 2 films are engineered to produce ferromagnetic insulating (FMI) films. From combined X-ray photoelectron spectroscopy, X-ray diffraction, and electron microscopy, the elimination of the insulator–metal (I–M) transition is shown to result from the creation of very small lateral coherence lengths (with the corresponding lateral size ∼ 3 nm (∼7 u.c.)) in the LBMO matrix, achieved by engineering a high density of CeO 2 nanocolumns in the matrix. The small lateral coherence length leads to a shift in the valence band maximum and reduction of the double exchange (DE) coupling. There is no “dead layer” effect at the smallest achieved lateral coherence length of ∼3 nm. The FMI behavior obtained by lateral dimensional tuning is independent of substrate interactions, thus intrinsic to the film itself and hence not related to film thickness. The unique properties of VAN films give the possibility for multilayer spintronic devices that can be made without interface degradation effects between the layers.

Robust ferromagnetic insulating and large exchange bias in LaMnO3:CoO composite thin films

“…In our opinion, the above two goals can be achieved simultaneously by introducing a second phase oxide into LMO films to construct an artificial interface that provides a multiscale platform for the transfer and reconstruction of the lattice, charge, spin and orbital states [30]. The question is that there are many types of interfaces, such as 0-3, 1-3, and 2-2 types [31][32][33][34][35], so how can an appropriate interface type be chosen to enhance and integrate FMI and EB effects? It is noted that 0-dimensional (0D) particles have a high specific surface; thus, the 0-3 type composite may have a relatively large interfacial area, which is positive not only for trapping defects at local isolated regions but also for preserving the interfacial strain and enhancing the interfacial magnetic interaction.…”