| 1. |
- Arnalds, Unnar, et al.
(författare)
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Thermalized ground state of artificial kagome spin ice building blocks
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:11, s. 112404-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We present a direct magnetic imaging study on the thermal macrospin ordering of artificial kagome spin ice building blocks. Using photoemission electron microscopy, employing x-ray magnetic circular dichroism, we are able to resolve the single domain magnetic nature of the macrospins and determine the states of the combined building block structures. The nano-patterning and material selection allows thermally activated magnetization reversal for the macrospins to occur. The ordering of the macrospins is dominated by the ground state, consistent with a thermal ground state ordering. This work paves the way for the realization of extended artificial spin ice structures exhibiting experimentally accessible thermal behavior
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| 2. |
- Kapaklis, Vassilios, et al.
(författare)
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Thermal fluctuations in artificial spin ice
- 2014
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 9:7, s. 514-519
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Tidskriftsartikel (refereegranskat)abstract
- Artificial spin ice systems have been proposed as a playground for the study of monopole-like magnetic excitations(1,2), similar to those observed in pyrochlore spin ice materials(3). Currents of magnetic monopole excitations have been observed's, 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(1,2). 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.
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| 3. |
- Slöetjes, Sam D., et al.
(författare)
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Effects of array shape and disk ellipticity in dipolar-coupled magnetic metamaterials
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:13
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional lattices of dipolar-coupled thin film ferromagnetic nanodisks give rise to emergent superferromagnetic (SFM) order when the spacing between dots becomes sufficiently small. In this paper, we define micron-sized arrays of permalloy nanodisks arranged on a hexagonal lattice. The arrays were shaped as hexagons, squares, and rectangles to investigate finite-size effects in the SFM domain structure for such arrays. The resulting domain patterns were examined using x-ray magnetic circular dichroism photoemission electron microscopy. At room temperature, we find these SFM metamaterials to be below their blocking temperature. Distinct differences were found in the magnetic switching characteristics of horizontally and vertically oriented rectangular arrays. The results are corroborated by micromagnetic simulations.
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