Antiferromagnetically exchange coupled CoFe/MgO/CoFe stacks

Exchange coupling in as-deposited and annealed magnetic trilayers Co
80
Fe
20
(CoFe)/MgO/Co
80
Fe
20
(CoFe) for MgO thickness spanning 0.45 to 4.5 nm has been studied. Antiferromagnetic exchange coupling behavior was observed in annealed CoFe/MgO/CoFe with 2.7-nm MgO insulating barrier. Interestingly, a transition from antiferromagnetic to nearly paramagnetic response to applied magnetic field was found around 520 °C—conceptually called as Neel temperature. Based on grazing incidence x-ray diffraction study, oxide phases of Co
3
O
4
, CoO, Fe
2
O
3
, Fe
3
O
4
, and CoFe
2
O
4
were found at CoFe/MgO interface. In the annealed CoFe/MgO interface, formation of CoO and CoFe
2
O
4
at the interface indicates they act as antiferromagnetic sources giving rise to the exchange-coupled antiferromagnetic/ferromagnetic (AFM/FM) interface.