Exchange coupling in NiO/CoFe2 and CoFe2O4/CoFe2 systems grown by pulsed laser deposition

NiO(30 nm)/CoFe2(5 nm) bilayers are grown by pulsed laser deposition on Si (001). After annealing under a magnetic field we observe an exchange bias of -86 Oe, corresponding to an exchange coupling of 0.06 erg/cm(2). While a similar exchange coupling is observed in NiO(30 nm)/CoFe2(5 nm)/SrTiO3(3 nm)/Ni80Fe20(5 nm)/Ta(5 nm), the stack SFMO(30 nm)/SrTiO3(3 nm)/CoFe2(5 nm)/NiO(30 nm)/Ta(5 nm) does not provide any exchange bias with NiO on the top electrode. Alternatively, we have used a ferrimagnetic oxide (CoFe2O4) as a bias layer of the top electrode. The stack SFMO(30 nm)/STO(3 nm)/CoFe2(5 nm)/CoFe2O4(70 nm) provides a shift of -70 Oe for the CoFe2(5 nm) layer, corresponding to an exchange coupling of 0.05 erg/cm(2). (c) 2006 American Institute of Physics.