Transport properties of resistive switching in Ag/Pr0.6Ca0.4MnO3/Al thin film structures

Thin films of Pr0.6Ca0.4MnO3 were prepared by pulsed laser deposition with an asymmetric pair of Ag and Al metal electrodes in order to study their resistive switching properties. The devices exhibited stable voltage controlled bipolar switching which proved to be reliable and non-volatile. The resistive states show a well-defined dependence on the write voltage, which was used to achieve several intermediate states, indicating that the devices could be utilized in hardware implementations of neuromorphic computing. The switching mechanism was attributed to the electric-field assisted migration of oxygen vacancies at the Al-electrode interface, resulting in a formation and modulation of a rectifying interfacial AIO(x) layer. The current-voltage characteristics were analyzed by means of the power exponent representation, which hinted to a device state dependent interplay of bulk-limited Poole-Frenkel conduction and interface-limited Schottky conduction. A deeper understanding of resistive switching characteristics in Ag/Pr0.6Ca0.4MnO3/Al will lead towards further advances in manganite-based neuromorphic circuits. (C) 2019 The Authors. Published by Elsevier B.V

Metastable ferromagnetic flux closure-type domains in strain relaxed Gd0.1Ca0.9MnO3 thin films

We have systematically studied the structural, electrical transport, and magnetic properties of Gd0.1Ca0.9MnO3 thin films in function of thickness, which ranged from 22 nm up to 220 nm. We have found that, although no strong substrate-induced strain was detected for any thickness, a sudden change in the electric transport properties was observed when the film thickness increases above 80 nm. While thinner samples are insulating in the whole temperature range, the samples thicker than 80 nm show a clear insulator-to-metal transition (IMT) at around 100 K. The IMT coincides with the appearance of a ferromagnetic phase that is absent in the thinner samples. We associate this change in behavior with a critical film thickness that induces a sudden change in domain configuration, from in-plane domain to a closed flux-type domain with out-of-plane orientations. These out-of-plane oriented domains are meta-stable ferromagnetic in nature and result in an IMT which is accompanied by a hysteretic magnetoresistance behavior.</p