Small-angle neutron scattering from superparamagnetic assemblies in binary CoGa alloys

Abstract

Small-angle diffuse neutron scattering measurements have been performed upon Co-rich CoGa alloys using the D11 diffractometer at ILL, Grenoble. These measurements, in conjunction with a re-investigation of the magnetic properties of the alloys, have revealed the existence of superparamagnetic behaviour associated with regions of correlated spins extending over approximately 60 AA. A relationship between the superparamagnetic assemblies and groups of Co atoms on the Ga sublattice is suggested by the differences in the observed scattering from alloys in the quenched and slow cooled conditions. Beyond a critical concentration of 55 at.% Co the onset of ferromagnetism is observed in the quenched alloys, although superparamagnetic behaviour is found to persist well into the ferromagnetic region.