Formation of Self-Organized Mn3O4 Nanoinclusions in LaMnO3 Films

Abstract

We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn 3 O 4 ) in a pristine perovskite matrix (LaMnO 3 ) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO 3 stoichiometric target by Pulsed Laser Deposition, the most favorable mechanism to accommodate Mn 2+ cations is the spontaneous segregation of self-assembled wedge-like Mn 3 O 4 ferrimagnetic inclusions inside a LaMnO 3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behavior. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn 3 O 4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (∼9 • ) c-axis tilting. Furthermore, a Ruddlesden-Popper La 2 MnO 4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn 3 O 4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions.

Epitaxial LaMnO3 films with remarkably fast oxygen transport properties at low temperature

“…The cell parameters used as reference are given in Table 1, they were measured by Ritter et al for LMO bulk samples obtained by annealing in Ar (d ¼ 0) and as prepared (d ¼ 0.07). 34 As schematically represented and explained by Pomar et al, 35 when grown on single crystal perovskite substrates and in order to accommodate the JT structural distortion at room temperature, stoichiometric LMO can present 2 different orientations, namely h110i and h001i, which correspond to the orthorhombic Pbnm c parameter in-plane or out-of-plane, respectively. 35 The d [110]LMO and d [001]LMO Mn-Mn distances, corresponding to these 2 orientations for the Pbnm orthorhombic LMO, are included in Table 1.…”

“…34 As schematically represented and explained by Pomar et al, 35 when grown on single crystal perovskite substrates and in order to accommodate the JT structural distortion at room temperature, stoichiometric LMO can present 2 different orientations, namely h110i and h001i, which correspond to the orthorhombic Pbnm c parameter in-plane or out-of-plane, respectively. 35 The d [110]LMO and d [001]LMO Mn-Mn distances, corresponding to these 2 orientations for the Pbnm orthorhombic LMO, are included in Table 1. For both STO and LAO substrates, a h110i orientation is favoured due to a better matching of lm and substrate cell parameters.…”

“…For both STO and LAO substrates, a h110i orientation is favoured due to a better matching of lm and substrate cell parameters. 35 For low oxygen content (d ¼ 0), due to the JT distortions, d [110]LMO is considerably higher compared to d [001]LMO , while the two distances become much closer in value for d ¼ 0.07.…”

“…Table 1 Pbnm orthorhombic cell parameters (a, b, c) reported for LaMnO 3+d bulk samples with different oxygen stoichiometry (d) 34 and d [hkl] Mn-Mn distances as calculated by Pomar et al 35…”

Ferroelectric-Ferromagnetic Heterostructures based on Sodium Substituted Lanthanum Manganite Thin films deposited on PMN-PT substrate by Pulsed Laser Deposition

“…In the case of LMO and its substitutes, structural distortion of the MnO 6 octahedra due to Jahn teller distortion takes place. The growth of LNMO film in either (1 0 0) or (1 1 0) direction is justified to accommodate this structural distortion to the substrate/crystal [23].…”