Revisiting neutron studies of reentrant spin glasses: the role of small-angle scattering1

The application is discussed of neutron methods to the study of reentrant spin glasses (RSGs), close to the transition towards a `canonical' spin glass (SG). The focus is on two emblematic systems, namely Au1-xFex and amorphous a-Fe1-xMnx. A set of experimental results is presented to highlight their peculiar static and dynamic properties. The role of small-angle neutron scattering (SANS) is stressed as an important tool to unravel the structure of these complex systems over mesoscopic length scales. Finally, recent SANS results performed under an applied magnetic field in the region of the RSG -> SG transition are presented. They show that vortex-like defects are present in the RSG region up to the critical line and vanish in the SG region. These defects, which develop only in a ferromagnetic medium, could be a key feature to probe the emergence of long-range magnetic order.

Automated summary

The application of neutron methods to the study of reentrant spin glasses and their transition to a canonical spin glass is discussed in this article. The focus is on two emblematic systems, namely Au1-xFex and amorphous a-Fe1-xMnx, and their unique static and dynamic properties are highlighted through experimental results. The role of small-angle neutron scattering (SANS) in unraveling the mesoscopic structure of these complex systems is emphasized. Recent SANS results performed under an applied magnetic field reveal the presence of vortex-like defects in the reentrant spin glass region up to the critical line, which vanish in the spin glass region. These defects, which only develop in a ferromagnetic medium, could be a key feature in probing the emergence of long-range magnetic order.