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Unusual magnetism in templated NiS nanoparticles.

Barry, L*; Holmes, J D*; Otway, D J*; Copley, M P*; Kazakova, O; Morris, M A* (2010) Unusual magnetism in templated NiS nanoparticles. J. Phys., Condens. Matter, 22 (7). 076001

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Nanostructured NiS was prepared by inclusion into anodic alumina templates. The resultant particles were found to be stoichiometric and highly crystalline. The particles displayed small particle superparamagnetism, and a low temperature (at 48 K (Tsg)) spin-freezing phenomenon (a spin-glass) and higher temperature (170 K) thermal blocking of small particle magnetic moment fluctuations were both observed for the first time for a sulfide material. Very unusually, these NiS materials are quite distinct from antiferromagnetic nanoparticulate sulfide materials, as they display a high temperature ferromagnetic-like phase. The saturation magnetization, the remanent magnetization, the coercivity and the ferromagnetic mass susceptibility were measured as 0.58 emu g-1 (at 100 K), 0.19 emu g-1, 219.5 Oe (at 170 K) and ~900 × 10-6 emu Oe-1 g-1 respectively and these are consistent with a moderately strong ferromagnetism. The materials had an unexpectedly high Curie temperature of 390 K. The decrease of the saturation magnetization value at 30 K suggests that the ferromagnetic response is a surface phenomenon and the high coercivity of the paramagnetic component well above Tsg suggests that the core can be described as superparamagnetic.

Item Type: Article
Subjects: Nanoscience
Nanoscience > Nano-Materials
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/4574

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