Neutron reflectivity on CoFe_(2)O_(4) exchange springs for spin valve applications

摘要

Insulating CoFe_(2)O_(4) is a candidate for biasing ferromagnetic layers in spin valves because it does not shunt current. Ferrimagnetic CoFe_(2)O_(4) pins the neighboring ferromagnetic layer via an exchange-spring mechanism. We have examined the field-dependent layer switching in a CoFe_(2)O_(4)/CoFe_(10) 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 CoFe_(2)O_(4) layer. This result contrasts with the expectation that the magnetic twist should reside in the soft layer in the field region of magnetic reversibility.