Neutron reflectivity on CoFe2O4 exchange springs for spin valve applications

Insulating CoFe2O4 is a candidate for biasing ferromagnetic layers in spin valves because it does not shunt current. Ferrimagnetic CoFe2O4 pins the neighboring ferromagnetic layer via an exchange-spring mechanism. We have examined the field-dependent layer switching in a CoFe2O4/CoFe10 bilayer using back/front polarized neutron reflectometry. A magnetic twist is evident in intermediate fields and gradually collapses as the field is increased. However, the twist is confined mostly to the interface or to the magnetically hard CoFe2O4 layer. This result contrasts with the expectation that the magnetic twist should reside in the soft layer in the field region of magnetic reversibility. (C) 2004 American Institute of Physics.