Structural and magnetic depth profiles of magneto-ionic heterostructures beyond the interface limit

• Published in: Nature communications 2016-07, Vol.7 (1), p.12264-8, Article 12264
• Main Authors: Gilbert, Dustin A., Grutter, Alexander J., Arenholz, Elke, Liu, Kai, Kirby, B. J., Borchers, Julie A., Maranville, Brian B.
• Format: Article
• Language: English
• Subjects: 140/146; 639/301/119/544; 639/301/119/995; 639/301/119/997; 639/925/357; Electric fields; Electronic properties and materials; Electrons; Ferromagnetism; Gadolinium; Heterostructures; Humanities and Social Sciences; Information storage; Interfaces; Magnetic measurement; Magnetic properties and materials; Magnetism; Magnetization; MATERIALS SCIENCE; Measurement techniques; multidisciplinary; Nanoscale materials; Oxidation; Oxygen; Phase transitions; Reflectometry; Science; Surfaces, interfaces and thin films; Valence; X-ray spectroscopy
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms12264

Electric field control of magnetism provides a promising route towards ultralow power information storage and sensor technologies. The effects of magneto-ionic motion have been prominently featured in the modification of interface characteristics. Here, we demonstrate magnetoelectric coupling moderated by voltage-driven oxygen migration beyond the interface in relatively thick AlO x /GdO x /Co(15 nm) films. Oxygen migration and Co magnetization are quantitatively mapped with polarized neutron reflectometry under electro-thermal conditioning. The depth-resolved profiles uniquely identify interfacial and bulk behaviours and a semi-reversible control of the magnetization. Magnetometry measurements suggest changes in the microstructure which disrupt long-range ferromagnetic ordering, resulting in an additional magnetically soft phase. X-ray spectroscopy confirms changes in the Co oxidation state, but not in the Gd, suggesting that the GdO x transmits oxygen but does not source or sink it. These results together provide crucial insight into controlling magnetism via magneto-ionic motion, both at interfaces and throughout the bulk of the films. Mechanisms allowing electrical manipulation of magnetic material possess potential applications in low power memory and sensor technologies. Here, the authors demonstrate the control of magnetic characteristics via voltage-driven migration of oxygen across a GdOx/Co interface, well into the bulk of the cobalt.