Analog control of La_0.5Sr_0.5FeO_3-δ electrical properties through oxygen deficiency induced magnetic transition

Switchability of materials properties by applying controlled stimuli such as voltage pulses is an emerging field of study with applicability in adaptive and programmable devices like neuromorphic transistors or non-emissive smart displays. One of the most exciting approaches to modulate materials performance is mobile ion/vacancy insertion for inducing changes in relevant electrical, optical, or magnetic properties, among others. Unveiling the interplay between changes in the concentration of mobile defects (like oxygen vacancies) and functional properties in relevant materials represents a step forward for underpinning the emerging oxide iontronics discipline. In this work, electrochemical oxide-ion solid-state pumping cells were fabricated for analog control of the oxygen stoichiometry in thin films of mixed ionic-electronic conductor La_0.5Sr_0.5FeO_3-δ. We demonstrate over more than four orders of magnitude electronic conductivity control at 50 °C within the same crystallographic phase through precise and continuous voltage control of the oxygen stoichiometry. We show that behind the modification of the transport properties of the material lays a paramagnetic-to-antiferromagnetic transition. We exploit such magnetoelectric coupling to show control over the exchange interaction between La_0.5Sr_0.5FeO_3-δ and a ferromagnetic Co layer deposited on top.