Polarized neutron reflectometry – a historical perspective

Born in the early 1980s to study magnetic films, polarized neutron reflectometry (PNR) has enjoyed growing popularity as witnessed by the number of instruments assembled at neutron research centers. PNR has proved its usefulness by providing information as diverse as the penetration depth of the magnetic field in superconductors and the absolute value of the magnetic moments in ultrathin ferromagnetic layers; yet its widest application has become the study of the magnetic configurations in multilayers. Two types of reflectometers have been constructed: time of flight and crystal analyzer. The relative merits of the two types are discussed in the light of present and future applications.