title: Thermal fluctuations in artificial spin ice.
abstract: Artificial spin ice systems have been proposed as a playground for the study of monopole-like magnetic excitations, similar to those observed in pyrochlore spin ice materials. Currents of magnetic monopole excitations have been observed, demonstrating the possibility for the realization of magnetic-charge-based circuitry. Artificial spin ice systems that support thermal fluctuations can serve as an ideal setting for observing dynamical effects such as monopole propagation and as a potential medium for magnetricity investigations. Here, we report on the transition from a frozen to a dynamic state in artificial spin ice with a square lattice. Magnetic imaging is used to determine the magnetic state of the islands in thermal equilibrium. The temperature-induced onset of magnetic fluctuations and excitation populations are shown to depend on the lattice spacing and related interaction strength between islands. The excitations are described by Boltzmann distributions with their factors in the frozen state relating to the blocking temperatures of the array. Our results provide insight into the design of thermal artificial spin ice arrays where the magnetic charge density and response to external fields can be studied in thermal equilibrium.
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden.
authors.forename: Vassilios
authors.identifier: 0000000261051659
authors.initials: V
authors.lastname: Kapaklis
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden.
authors.forename: Unnar B
authors.initials: UB
authors.lastname: Arnalds
authors.affiliation: 1] Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland [2] Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Alan
authors.initials: A
authors.lastname: Farhan
authors.affiliation: 1] Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland [2] Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Rajesh V
authors.initials: RV
authors.lastname: Chopdekar
authors.affiliation: Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Ana
authors.initials: A
authors.lastname: Balan
authors.affiliation: Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, California 94720, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Scholl
authors.affiliation: 1] Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland [2] Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Heyderman
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden.
authors.forename: Björgvin
authors.initials: B
authors.lastname: Hjörvarsson
mesh_terms: D007053:Ice; D060526:Magnetic Fields; D013113:Spin Labels; D014867:Water / Q000737:chemistry*
chemical_list: D007053:Ice; D013113:Spin Labels; D014867:Water