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We present experimental results of electrical resistivity (ρ), magnetoresistance (MR), Seebeck coefficient (S), and magnetic susceptibility (χ) experiments at high temperature on the spinel Mn2-xV1+xO4 series with x=0, 13, and 1, prepared by solid state reaction. The Rietveld analysis of neutron powder diffraction (NPD) patterns confirm the expected cubic symmetry (SG: Fd-3m) with cell parameters around 8.5 Å. We also precisely calculate the distribution of Mn/V cations, in the tetrahedral and octahedral sites, for the whole series showing an important degree of inversion. The magnetic susceptibility and electrical transport properties show ferrimagnetic and semiconductor behaviors, respectively. A large difference detected between the activation energies for S and ρ indicates the presence of small polarons and the temperature dependence of ρ is well fitted with the nonadiabatic polarons model. All the samples present positive MR at room temperature, in particular, the highest value (around 1%) was observed in the MnV2O4 sample. [ABSTRACT FROM AUTHOR]

Mechanical control of electrical properties in complex heterostructures, consisting of magnetic FeO x nanoparticles on top of manganite films, is achieved using atomic force microscope (AFM) based methods. Under applied pressure of the AFM tip, drop of the electrical conductivity is observed inducing an electrically insulating state upon a critical normal load. Current and surface potential maps suggest that the switching process is mainly governed by the flexoelectric field induced at the sample surface. The relaxation process of the electrical surface potential indicates that the diffusion of oxygen vacancies from the bulk of the manganite films towards the sample surface is the dominant relaxation mechanism. The magnetic FeO x nanoparticles, staying attached to the sample surface after the rubbing, protect the underlying manganite films and provide stability of the observed resistive switching effect. The employed mechanical control gives a new freedom in the design of resistive switching devices since it does not depend on the film thickness, and biasing is not needed., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)