Polarised neutron reflectometry for GMR sensors optimization

Neutron reflectometry with spin analysis has allowed us to perform selective hysteresis loops of each magnetic layer in GMR spin valves. The intensities now available on reflectometers and the advances of modelling give the possibility to perform a very precise analysis of the magnetic configuration even in complex systems with five different magnetic layers. Results obtained on GMR spin valves show a rather complex behaviour of the free layer as a function of the magnetic field. The NiFe soft layer exhibits a non-homogeneous rotation which cannot be observed in transport measurements. This non-homogeneous rotation explains the necessity of a rather thick soft layer to avoid 1/f magnetic noise in GMR sensors.