Surface Nanostructures in Manganite Films

Abstract

Ultrathin manganite films are widely used as active electrodes in organic spintronic devices. In this study, a scanning tunnelling microscopy (STM) investigation with atomic resolution revealed previously unknown surface features consisting of small non-stoichiometric islands. Based upon this evidence, a new mechanism for the growth of these complex materials is proposed. It is suggested that the non-stoichiometric islands result from nucleation centres that are below the critical threshold size required for stoichiometric crystalline growth. These islands represent a kinetic intermediate of single-layer growth regardless of the film thickness, and should be considered and possibly controlled in manganite thin-film applications.

Surface engineering with Ar+/O2+ ion beam bombardment: Tuning the electronic and magnetic behavior of Ni80Fe20/La0.7Sr0.3MnO3/SrTiO3(001) junctions

“…4(d)] implies that the chemical composition and/or stoichiometry of the interfacial layers are different between the two bilayer samples (also different from the intrinsic interfacial layer on a nonbombarded NiFe/LSMO bilayer), depending on the ion species used (Ar + or O 2 + ). The interfacial layer could be due to the formation of two-dimensional non-stoichiometric islands; 19 and/or La-rich and Mn-rich oxide phases as reported previously. 5 In the present case, the formation of interfacial antiferromagnetic phases, such as Mn, MnO, or NiO, could give rise to the observed H ex , whereas the enhanced H C could result due to the formation of harder ferrimagnetic phases like Mn 3 O 4 or Fe 3 O 4 or possible intermixed phases such as NiFeMn or NiFeO.…”

“…2, and in good agreement with our previous work). 19,20 However, the non-bombarded NiFe/LSMO bilayer exhibits quite a different shape of MR in which the two peaks are more separated with a symmetric step in each branch, as shown in Fig. 9(b).…”

“…A way to induce a change in the surface layer has been proposed recently by using ion-beam bombardment techniques: both in situ bombardment with low-energy (∼100 eV) Ar + or O 2 + /Ar + mixtures [12][13][14][15][16][17] and ex situ post-deposition irradiation with high-energy (∼10 keV) O +18 have been successfully applied. In this work, we present the impact of low-energy ex situ Ar + and O 2 + ion-beam bombardment on the LSMO surface, to etch and modify the stoichiometry of the native LSMO surface layer 19 and how such an intrinsic layer can be exploited in Ni 80 Fe 20 (NiFe)/LSMO junctions to obtain a MTJ device. The NiFe/LSMO bilayers were structurally characterized by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), and magnetically by SQUID magnetometry, magneto-transport, and polarized neutron reflectometry (PNR) to evidence the impact of LSMO bombardment on the overall magnetotransport properties of the junction.…”

Surface‐Driven Magnetotransport in Perovskite Nanocrystals

“…The properties of these open surface electrodes exposed to atmosphere and solvents are however hard to reconcile with those of epitaxial (buried) interfaces in thin films grown under stringent high vacuum or controlled oxygen pressure conditions. Especially, quantitative measurements from surface studies [6,7] require measurements over large areas due to the limited sensitivity of experimental tools, so that nanoscale variations of electrical transport properties are not reported, [8] thus leaving an open question: how does spin transport occur at the surfaces and interfaces of LSMO nanostructures and how does it impact hybrid spintronics?…”

Effects of strain relaxation in Pr0.67Sr0.33MnO3 films probed by polarization dependent X-ray absorption near edge structure

“…Manganites are potential candidates for resistance random access memories (RRAM) in the next generation of non-volatile memories345. The electronic structure plays an important role4 in resistance switching of RRAM678.…”