Thermally and field-driven mobility of emergent magnetic charges in square artificial spin ice

• Published in: Scientific reports Vol. 9; no. 1; p. 15989
• Main Authors: Morley, Sophie A., Porro, Jose Maria, Hrabec, Aleš, Rosamond, Mark C., Venero, Diego Alba, Linfield, Edmund H., Burnell, Gavin, Im, Mi-Young, Fischer, Peter, Langridge, Sean, Marrows, Christopher H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.11.2019; Nature Publishing Group
• Subjects: 142/126; 142/136; 639/301/357/997; 639/766/119/997; 639/925/930/2735; Arrays; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Drift; Energy; High temperature; Humanities and Social Sciences; Laboratories; Magnetic fields; Microscopy; Mobility; multidisciplinary; Nanotechnology; Science; Science (multidisciplinary); Statistical mechanics
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-52460-7

Designing and constructing model systems that embody the statistical mechanics of frustration is now possible using nanotechnology. We have arranged nanomagnets on a two-dimensional square lattice to form an artificial spin ice, and studied its fractional excitations, emergent magnetic monopoles, and how they respond to a driving field using X-ray magnetic microscopy. We observe a regime in which the monopole drift velocity is linear in field above a critical field for the onset of motion. The temperature dependence of the critical field can be described by introducing an interaction term into the Bean-Livingston model of field-assisted barrier hopping. By analogy with electrical charge drift motion, we define and measure a monopole mobility that is larger both for higher temperatures and stronger interactions between nanomagnets. The mobility in this linear regime is described by a creep model of zero-dimensional charges moving within a network of quasi-one-dimensional objects.