Abstract
Electric-field-driven ion migration can significantly modulate the electric and magnetic properties of solids, creating novel functionalities useful for advanced electromagnetic devices. Earlier works have used vertically stacked structures for this purpose, in which the redox process results from ion migration driven by a vertical electric field through the interfaces. However, the existence of the interfaces between the dissimilar layers causes the oxidation and reduction processes to have high and asymmetric energy barriers, which means that a large electric field is required to control the devices. Here, we show that in a partially oxidized single GdOx wire using a lateral electric field configuration, low and symmetric energy barriers for the oxidation and reduction processes can be achieved. We provide evidence that the redox process is the result of the lateral motion of oxygen ions by directly visualizing the electric-field-driven real-time ionic motion using an optical microscope. An electric field as low as 105 V/m was able to drive oxygen ions at room temperature, allowing controllable modulation of the electrical resistance using a lateral electric field. A large negative magnetoresistance was also observed in the GdOx wire, and its magnitude was significantly enhanced up to 20% at 9 T through oxygen ion control. Our results suggest that the electrical and magnetic properties of single GdOx can be efficiently controlled through oxygen ion motion driven by a lateral electric field, which paves the way for fully functional electromagnetic devices such as artificial synapses.
Highlights
Gadolinium (Gd) is one of the most interesting rareearth metals
We investigate the possibility of utilizing oxygen ions in a single GdOx device instead of heterostructures
To provide more direct evidence, we measured the real-time color change of TaOx/GdOx using an optical microscope because the change in oxygen ion concentration is reflected by changes in the optical contrast[20]
Summary
Gadolinium (Gd) is one of the most interesting rareearth metals It exhibits fascinating electrical and magnetic properties[1,2,3,4] and has practical value in applications including hydrogen storage[5] and CMOS technology as gate electrodes[6] and spintronics[7,8,9,10,11,12]. One distinctive property of Gd is that it is very oxidized, forming oxide compounds, GdOx. Since the oxygen ions are mobile in GdOx13,14, it has been used as an oxygen source (or sink) in ferromagnet/GdOx heterostructures[14,15,16,17,18,19].
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