Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites

A full characterization of phase separation and the competition between phases is necessary for a comprehensive understanding of strongly correlated electron materials, such as under-doped high-temperature superconductors, complex oxide heterojunctions, spinels, multiferroics, rare-earth ferroelectric manganites and mixed-valence manganites in which phase competition is the dominant mechanism governing the insulator-metal (IM) transition and the associated colossal magnetoresistance effect. Thin films of strongly correlated electron materials are often grown epitaxially on planar substrates and typically have anisotropic properties that are usually not captured by edge-mounted four-terminal electrical measurements, which are primarily sensitive to inplane conduction paths. We present an experimental study of anisotropic transport in phase-separated manganite thin films by using an unconventional arrangement of contact electrodes that enables the simultaneous determination of colossal magnetoresistance associated with d.c. transport parallel to the film substrate and colossal magnetocapacitance associated with a. c. transport in the perpendicular direction. We distinguish two distinct direction-dependent IM transitions and find a dielectric response that collapses onto a scale-invariant dependence over a large range of frequency, temperature and magnetic field.