| Autor: |
Morley SA; School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK. samorley@ucsc.edu.; Department of Physics, University of California, Santa Cruz, California, 95064, USA. samorley@ucsc.edu., Riley ST; School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK., Porro JM; ISIS Neutron and Muon Source, STFC, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK.; BCMaterials, Basque Center for Materials, Applications and Nanostructures, 48160, Derio, Spain., Rosamond MC; School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK., Linfield EH; School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK., Cunningham JE; School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK., Langridge S; ISIS Neutron and Muon Source, STFC, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK., Marrows CH; School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK. c.h.marrows@leeds.ac.uk. |
| Abstrakt: |
Artificial spin ices (ASI) are arrays of single domain nano-magnetic islands, arranged in geometries that give rise to frustrated magnetostatic interactions. It is possible to reach their ground state via thermal annealing. We have made square ASI using different FePd alloys to vary the magnetization via co-sputtering. From a polarized state the samples were incrementally heated and we measured the vertex population as a function of temperature using magnetic force microscopy. For the higher magnetization FePd sample, we report an onset of dynamics at T = 493 K, with a rapid collapse into >90% ground state vertices. In contrast, the low magnetization sample started to fluctuate at lower temperatures, T = 393 K and over a wider temperature range but only reached a maximum of 25% of ground state vertices. These results indicate that the interaction strength, dynamic temperature range and pathways can be finely tuned using a simple co-sputtering process. In addition we have compared our experimental values of the blocking temperature to those predicted using the simple Néel-Brown two-state model and find a large discrepancy which we attribute to activation volumes much smaller than the island volume. |
