Conducting domain wall networks in TbMnO3

SALVERDA, MART; R. HAMMING-GREEN; C. P. QUINTEROS; P. NUKALA; ACEVEDO, W ROMÁN; D. RUBI; S. FAROKHIPOOR; D RUBI

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Conferencia; MEMRISYS; 2019

Epitaxial thin films of orthorhombic, antiferromagnetic TbMnO3 grown on SrTiO3 substrates contain perfectly vertical, atomically thin domain walls[1]. In these walls, every other terbium atom is replaced by a manganese atom, leading to a chemical environment that is quite different from that of the domains and displaying ferromagnetic interactions localized at the walls. As it happens in other perovskite thin films with ferroelastic domain walls [2,3,4], it is expected that the electrical properties of the domains walls also deviate from those of the bulk. Most often, the conductivity enhancement is due to defect migration and local reduction of the Schottky barrier close to the domain walls. In the case of TbMnO3 on SrTiO3, the presence of ferromagnetism at the walls suggests an increase of their metallicity, In this work we investigate the electrical properties of these films when they are grown on conducting Nb-doped SrTiO3 substrates. The interface between the TbMnO3 film and the conductive substrate forms a p-n junction. We fabricate macroscopic 3-terminal geometry electrodes and guard-ring electrodes to measure DC I-V, curves and we fit the data to the Shockley diode equation including a resistance in series. We use a model for the resistance of the films, based on domain walls density, film thickness and other structural parameters, to obtain a value of the sheet resistance of these walls. We hope that this work will help to understand the resistive switching mechanism that was observed in TbMnO3/Nb:SrTiO3 devices [5] and, thus, to provide the first steps towards utilizing self-assembled conductive domain walls as memristive networks.