Hydrogen found to transmit magnetism

A team of chemists and physicists at the Universities of Liverpool and Oxford have shown that hydrogen transmits magnetism. This discovery could be the first step to a new class of magnetic materials, and opens up a new field of chemistry.

The team, headed by Professor Matthew Rosseinsky of the Department of Chemistry, University of Liverpool, and including Dr Stephen Blundell of the University of Oxford, has prepared a new magnetic oxide material in which for the first time the dominant magnetic interaction is mediated by a negatively-charged hydrogen atom, known as a hydride ion. The work is presented in a paper to be published in Science on 8 March 2002.

Many types of magnetic oxides have been prepared before which show important magnetic, conducting and even superconducting properties, but the new material, LaSrCoO3H0.7, is the first where oxide and hydride ions coexist.

The magnetic properties were confirmed by measurements of the new material using particles known as muons. ‘Muons behave like tiny gyroscopes and spin round when they experience a magnetic field’, Dr Stephen Blundell of Oxford University explained. ‘When implanted in the new material, we found that they carried on spinning round as we warmed the sample from a degree above absolute zero to room temperature, demonstrating that the sample was magnetic over the whole region. That was a surprise because without the hydrogen in there, we would have expected the oxide chains to lose their magnetism at all but the lowest temperatures.’

The new oxide hydride LaSrCoO3H0.7 adopts an unprecedented structure in which oxide chains are bridged by hydride anions to form a two-dimensional extended network. The metal centers are strongly coupled by their bonding with both oxide and hydride ligands to produce
magnetic ordering up to at least 350 K. The synthetic route is sufficiently general to allow the prediction of a new class of transition metal-containing electronic and magnetic materials.

Professor Rosseinsky said: ‘The chemistry leading to this compound was totally unexpected – before this work, most chemists would not have believed that anyone could synthesise a material with this composition.’