High-Tc Magnets in a Series of Substituted Pyridinium−FePS3 Layered Intercalates

A series of new FePS3 layered intercalation compounds having the general formula Fe1-xPS3G2x (where G stands for a monocation) has been prepared by cation exchange with several pyridinium derivatives. The occurrence of intralayer Fe2+ vacancies is evidenced by 57Fe Mössbauer spectroscopy. The magnetic properties of these well-crystallized intercalates are shown to depend dramatically on the nature of the guest species. Some intercalates remain antiferromagnets as in pristine FePS3, but those with pyridinium, N-methylpyridinium, and methylviologen as the guest species acquire a spontaneous magnetization below a critical temperature which can be as high as 88 K. The magnetization of the methylviologen intercalate is particularly strong. The magnetization in all cases displays a strong remanance due to single ion anisotropy of the Fe2+ ions and to the Ising character of the magnetic interaction.