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 published in Science on Friday (March 8).

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 in which 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. Blundell 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 synthesize a material with this composition."

The work was funded by the Engineering and Physical Sciences Research Council of the UK, and the Petroleum Research Foundation of the American Chemical Society. The muon-spin rotation measurements were performed at the Paul Scherrer Institute, Villigen, Switzerland.

The scientists involved in the team are Mike Hayward, Eddie Cussen, John Claridge, Mario Bieringer, Matthew Rosseinsky, and Chris Kiely of the Chemistry Department, Liverpool University, UK, Stephen Blundell and Ishbel Marshall of the Clarendon Laboratory, Oxford University Department of Physics, and Francis Pratt of the Rutherford Appleton Laboratory.

(Reference: Science 8 March 2002, The hydride anion in an extended transition metal oxide array - LaSrCoO3H0.7.)

11-Mar-2002