| 1. |
- Qviller, A. J., et al.
(author)
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Direct observation of magnetic proximity effects in amorphous exchange-spring magnets by neutron reflectometry
- 2020
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In: Physical Review Materials. - 2475-9953. ; 4:10
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Journal article (peer-reviewed)abstract
- In this paper, we report a direct observation of a magnetic proximity effect in an amorphous thin-film exchange-spring magnet by the use of neutron reflectometry. The exchange-spring magnet is a trilayer consisting of two ferromagnetic layers with high T-c separated by a ferromagnetic layer, which is engineered to have a significantly lower T-c than the embedding layers. This enables us to measure magnetization depth profiles at which the low-T-c material is in a ferromagnetic or paramagnetic state, while the embedding layers are ferromagnetic. A clear proximity effect is observed 7 K above the intrinsic T-c of the embedded layer, with a range extending 50 angstrom.
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| 2. |
- Magnus, Fridrik, et al.
(author)
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Tuneable exchange-spring stiffness in amorphous magnetic trilayer structures
- 2021
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In: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 33:44
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Journal article (peer-reviewed)abstract
- We investigate the magnetic properties of amorphous Sm10Co90/Co-60(Al70Zr30)(40)/Co-85(Al70Zr30)(15) exchange-spring magnet trilayers. The magnetically soft Co-85(Al70Zr30)(15) layer is coupled to the magnetically hard Sm10Co90 layer through the weakly magnetic low-T (c) Co-60(Al70Zr30)(40) spacer layer. The strength of the coupling can be controlled with temperature and the coupling persists above the intrinsic T (c) of the spacer layer due to a long-range magnetic proximity effect. Polarized neutron reflectivity is used to examine the magnetic profile of the trilayers during magnetization reversal. A two-step switching occurs, with the switching angle of the soft layer strongly dependent on the strength of the coupling. In the strong coupling regime a magnetic state can be achieved where the soft layer magnetization is perpendicular to the hard layer whereas in the weak coupling regime the soft layer reverses fully.
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| 3. |
- Stopfel, Henry, et al.
(author)
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Multiple energy scales in mesospin systems : The vertex-frustrated Saint George lattice
- 2021
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In: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 5:11
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Journal article (peer-reviewed)abstract
- The interplay between topology and energy hierarchy plays a vital role in the collective magnetic order in artificial ferroic systems. Here we investigate, experimentally, the effect of having one or two activation energies of interacting Ising-like magnetic islands—mesospins—in thermalized, vertex-frustrated lattices. The thermally arrested magnetic states of the elements were determined using synchrotron-based magnetic microscopy after cooling the samples from temperatures above the Curie temperature of the material. Statistical analysis of the correlations between mesospins across several length scales reveals changes in the magnetic order, reflecting the amount of ground state plaquettes realized for a vertex-frustrated lattice. We show that the latter depends on the presence, or not, of different activation energies.
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| 4. |
- Thorarinsdottir, K. A., et al.
(author)
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Finding order in disorder : Magnetic coupling distributions and competing anisotropies in an amorphous metal alloy
- 2022
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In: APL Materials. - : American Institute of Physics (AIP). - 2166-532X. ; 10:4
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Journal article (peer-reviewed)abstract
- Amorphous metals have unusual magnetic properties that arise due to the disordered atomic arrangement. We show that Co-x(Al70Zr30)(100-x) (65 < x < 92 at.%) amorphous alloys have a distribution in the local magnetic coupling and ordering temperature, which can be explained by nanoscale composition variations. We use competing anisotropies induced by the substrate and an applied field during growth to probe the Co concentration distribution. Only regions with high enough Co concentration develop a magnetic anisotropy along the magnetic field during growth, whereas regions of low Co concentration have an anisotropy dictated by the substrate. A Gaussian distribution in the Co concentration of width 5.1 at.% is obtained from the variation in anisotropy. The results demonstrate the importance of composition variations for emergent magnetic properties and have far reaching implications for the properties of disordered materials in general.
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