title: Thermally induced magnetic relaxation in square artificial spin ice.
abstract: The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice - we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: M S
authors.initials: MS
authors.lastname: Andersson
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: S D
authors.initials: SD
authors.lastname: Pappas
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Stopfel
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Östman
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973, USA.
authors.forename: A
authors.initials: A
authors.lastname: Stein
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Nordblad
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Mathieu
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Hjörvarsson
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: V
authors.initials: V
authors.lastname: Kapaklis