Studies of deposition order anomaly of exchange coupling in bilayers and trilayers of NiFe and CoO

The temperature dependence of the exchange field and coercivity and the effect of deposition order have been studied in a series of bilayer (NiFe/CoO and CoO/NiFe) and trilayer (NiFe/CoO/NiFe) films. A profound difference in the exchange field temperature behavior was observed in samples with NiFe deposited on top of CoO compared to samples with CoO deposited on top of NiFe. When CoO is on top of NiFe, the exchange field follows a linear temperature dependence, while for samples with NiFe on top of CoO, the exchange field has a plateau followed by a rapid decrease. These distinct temperature dependences are reproduced in the NiFe/CoO/NiFe trilayer which contains both geometries. Transmission electron microscopy has been employed to study the interface between the NiFe and CoO layers. (C) 1997 American Institute of Physics.