Magnetocaloric effect in layered metal hydroxides

Igoshin, Aleksandr (2025) Magnetocaloric effect in layered metal hydroxides. Research Project, Chemistry.

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Abstract

This research investigates the synthesis, morphology and magnetic properties of monometallic layered double hydroxides with focus on layered ferromagnetic materials with high magnetic entropy change for hydrogen liquefaction while offering a more sustainable alternative to rare-earth based materials. Adapting a previously discovered procedure in the group, a mixture of two phases of air sensitive manganese based layered double hydroxides was synthesised via solvent evaporation. Both compositions exhibit antiferromagnetic ordering with transitions temperatures within operational ranges for hydrogen liquefaction. Green Rust was obtained via solvothermal treatment from iron chloride hexahydrate and sodium acetate in glycerol. While intercalation of lactate anions improved the stability of metal centers to oxidation in air, the in-plane ordering is antiferromagnetic based on Curie-Weiss fitting. Implementation of lactate anion for air stability proved effective in synthesis of an iron based layered simple hydroxide from iron sulfate heptahydrate and sodium hydroxide in glycerol. The solvothermal treatment and subsequent washing with ethanol yielded an air stable dark green powder exhibiting antiferromagnetic ordering below 45 K. Attempting to synthesize ferromagnetic Co5(OH)6(SeO4)2 4 H2O was not successful as the desired structure could not be obtained. The magnetic interactions in the material are dominated by superexchange leading to an antiferromagnetic transition at 20 K.

Item Type:	Thesis (Research Project)
Supervisor name:	Blake, G.R.
Degree programme:	Chemistry
Thesis type:	Research Project
Language:	English
Date Deposited:	15 Jul 2025 07:41
Last Modified:	15 Jul 2025 07:41
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/36175

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