Javier Tornos

Developing electronic devices capable of reproducing synaptic functionality is essential in the context of implementing fast, low‐energy consumption neuromorphic computing systems. Hybrid ionic/electronic three‐terminal synaptic transistors are promising as efficient artificial synapses since they can process information and learn simultaneously. In this work, an electrolyte‐gated synaptic transistor is reported based on an ultra‐thin epitaxial La 0.7 Sr 0.3 MnO 3 (LSMO) film, a half‐metallic system close to a metal‐insulator transition. The dynamic control of oxygen composition of the manganite ultra‐thin film with voltage pulses applied through the gate terminal allows reversible modulation of its electronic properties in a non‐volatile manner. The conductance modulation can be finely tuned with the amplitude, duration, and number of gating pulses, providing different alternatives to gradually update the synaptic weights. The transistor implements essential synaptic features such as excitatory postsynaptic potential, paired‐pulse facilitation, long‐term potentiation/depression of synaptic weights, and spike‐time‐dependent plasticity. These results constitute an important step toward the development of neuromorphic computing devices leveraging the tunable electronic properties of correlated oxides, and pave the way toward enhancing future device functionalities by exploiting the magnetic (spin) degree of freedom of the half metallic transistor channel.

Generation, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half‐metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La 1− x Sr x MnO 3 (LSMO) manganites are considered as promising candidates for their robust half‐metallic ground state, Curie temperature above room temperature ( T c = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross‐shape nanowires with single‐domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non‐adiabatic processes at spin textures despite the strong Hund coupling to the localized t 2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors.