Driving Curie temperature towards room temperature in the half-metallic ferromagnet K2Cr8O16by soft redox chemistry

Autor:	Emilio Morán, Ivan Pirrotta, Javier Fernández-Sanjulián, Flaviano García-Alvarado, Elena Gonzalo, Alois Kuhn, M.A. Alario-Franco
Rok vydání:	2012
Předmět:	Inorganic Chemistry chemistry.chemical_compound Ferromagnetism Oxidation state Chemistry Hollandite Oxidizing agent Inorganic chemistry Curie temperature Redox Nitrosonium tetrafluoroborate Soft chemistry
Zdroj:	Dalton Trans.. 41:1840-1847
ISSN:	1477-9234 1477-9226
DOI:	10.1039/c1dt11558h
Popis:	The half-metallic ferromagnet K(2)Cr(8)O(16) with the hollandite structure has been chemically modified using soft chemistry methods to increase the average oxidation state of chromium. The synthesis of the parent material has been performed under high pressure/high temperature conditions. Following this, different redox reactions have been carried out on K(2)Cr(8)O(16). Oxidation to obtain potassium-de-inserted derivatives, K(2-x)Cr(8)O(16) (0 ≤x≤ 1), has been investigated with electrochemical methods, while the synthesis of sizeable amounts was achieved chemically by using nitrosonium tetrafluoroborate as a highly oxidizing agent. The maximum amount of extracted K ions corresponds to x = 0.8. Upon oxidation the hollandite structure is maintained and the products keep high crystallinity. The de-insertion of potassium changes the Cr(3+)/Cr(4+) ratio, and therefore the magnetic properties. Interestingly, the Curie temperature increases from ca. 175 K to 250 K, getting therefore closer to room temperature.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::c98b92bdf329dbcee9d3cff815a24712 https://doi.org/10.1039/c1dt11558h Zobrazit plný text záznamu