| 1. |
- Arnalds, Unnar B., et al.
(författare)
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Thermal transitions in nano-patterned XY-magnets
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:4, s. 042409-
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated ultra-thin disc shaped islands wherein shape anisotropy confines the moment to the island plane, creating XY-like superspins. At low temperatures, the superspins are blocked, and, as the temperature is increased, they undergo a transition into a superparamagnetic state. The onset of this dynamic superspin state scales with the diameter of the islands, and it persists up to a temperature governed by the intrinsic ordering temperature of the island material defining a range in temperature in which dynamic behavior of the magnetic islands can be obtained.
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| 2. |
- Kapaklis, Vassilios, et al.
(författare)
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Melting artificial spin ice
- 2012
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 035009-
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Tidskriftsartikel (refereegranskat)abstract
- Artificial spin ice arrays of micromagnetic islands are a means of engineering additional energy scales and frustration into magnetic materials. Here we demonstrate a magnetic phase transition in an artificial square spin ice and use the symmetry of the lattice to verify the presence of excitations far below the ordering temperature. We do this by measuring the temperature dependent magnetisation in different principal directions and comparing with simulations of idealised statistical mechanical models. Our results confirm a dynamical pre-melting of the artificial spin ice structure at a temperature well below the intrinsic ordering temperature of the island material. We thus create a spin ice array that has real thermal dynamics of the artificial spins over an extended temperature range.
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| 3. |
- Karimipour, Masoud, et al.
(författare)
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Nanoparticles of Ni/NiO embedded in TiO(2) synthesized by the complex-polymer sol-gel method
- 2011
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 84:3, s. 035702-
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Tidskriftsartikel (refereegranskat)abstract
- Ni-doped TiO(2) nanoparticles were synthesized by the non-hydrous complex-polymer sol-gel method. Titanium isopropoxide was used as precursor and acetyl acetone (AcAc) and citric acid were used as polymer and complex agent, respectively. A series of Ni(x) : Ti(1-x)O(2) samples with x = 0.01, 0.03, 0.05 and 0.10 were prepared and subsequently annealed at 400, 600 and 800 degrees C. The structural and magnetic properties of Ni(x) : Ti(1-x)O(2) were studied by means of x-ray diffraction (XRD) and dc magnetometery. Samples annealed at 400 degrees C attained a particle size of 12 nm with structural phases of anatase, rutile and cubic NiO. From the blocking temperatures of the zero-field-cooled and field-cooled measurements, similar particle sizes (as from XRD) were obtained. The presence of ferro- and antiferromagnetic (AFM) interactions further confirms that the particles have different structural compositions. At 800 degrees C the particles have grown to about 30 nm with either a rutile or NiTiO(3)-type structure. The presence of NiTiO(3) is also seen in the magnetic measurements, which show the characteristic AFM peak at 23 K.
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