Correlation of structural and magnetic properties in oxides containing 1-D chains of MnO6 octahedra

Purely ferromagnetic (FM) oxides are uncommon but we recently reported FM behaviour in a mineral induced by quite small magnetic fields. This ability relates to the presence of chains of linked MnO6 octahedra which prefer FM order, whereas order between the chains is frustrated. The this combination gives unique properties and energy-efficient refrigeration at temperatures capable of liquefying hydrogen gas. This proposal will study materials containing similar chains but different ordering schemes between the chains. Some are completely FM in character at low temperature whilst one is antiferromagnetic. The FM materials show unusual magnetic behaviour suggesting some FM clusters above the ordering temperature and the possibility of excellent refrigeration properties but over a larger temperature range than our mineral. Properties will be measured at various magnetic fields.