³He nuclear magnetism

Nuclear spin ordering in solid ³He is observed in 3 different phases: in the bcc - solid at pressures around 2.4MPa two presumably antiferromagnetic phases are observed. In the high pressure hcp - solid ferromagnetic order is expected. Nuclear spin order in solid ³He is caused by a unique interaction mechanism: multiple particle exchange processes are by far dominant.

The central aim of the network activity is the direct investigation of the microscopic nuclear spin structures and the underlying interactions by means of neutron diffraction techniques. It will construct and, where necessary, develop the instruments and experimental techniques to undertake this study.

Major scientific objectives are the determination of ³He crystal growth conditions, the investigation of magnetic order both in the chemical bcc and hcp - phase and a direct determination of interaction parameters using high resolution, quasi-elastic neutron diffraction. The anticipated results will be analysed at one network node to establish a relation between ordering phenomena and the underlying interactions.