Oxygen Impurities Link Bistability and Magnetoresistance in Organic Spin Valves

TLDR: Variable oxygen doping of the organic molecules represents the key element for correlating bistability and MR, and the measurements provide the first experimental evidence in favor of the impurity-driven model describing the spin transport in organic semiconductors in similar devices.

Abstract: Vertical crossbar devices based on manganite and cobalt injecting electrodes and a metal-quinoline molecular transport layer are known to manifest both magnetoresistance (MR) and electrical bistability. The two effects are strongly interwoven, inspiring new device applications such as electrical control of the MR and magnetic modulation of bistability. To explain the device functionality, we identify the mechanism responsible for electrical switching by associating the electrical conductivity and the impedance behavior with the chemical states of buried layers obtained by in operando photoelectron spectroscopy. These measurements revealed that a significant fraction of oxygen ions migrate under voltage application, resulting in a modification of the electronic properties of the organic material and of the oxidation state of the interfacial layer with the ferromagnetic contacts. Variable oxygen doping of the organic molecules represents the key element for correlating bistability and MR, and our measurements provide the first experimental evidence in favor of the impurity-driven model describing the spin transport in organic semiconductors in similar devices.

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In this paper, the authors focus their attention to the prototypical device composed of metal-quinoline injectors with bistable sensors and demonstrate that resistive switching ( RS ) behavior in organic devices has excited substantial attention because, in addition to the well-known aspects of high performance and low volatility that are inherent to RS memory, the use of organic components would yield easy-to-process, flexible devices.