Thermal Stability of FePt-Based Exchange Coupled Composite Films

Three series of
$L1_{0}$
-FePt based exchange coupled composite (ECC) films
$L1_{0}$
-FePt/Fe,
$L1_{0}-{\rm FePt}/[{\rm Co/Ni}]_{\rm N}$
and
$L1_{0}-{\rm FePt}/[{\rm Co/Pt}]_{\rm N}$
, with different magnetization configurations, on MgO substrates are studied. Though all series of samples show similar dependences of coercivity on the soft layer thickness, their thermal stabilities are much different. The perpendicular ECC film of
$L1_{0}-{\rm FePt}/[{\rm Co/Ni}]_{\rm N}$
shows a higher thermal stability than that of in-plane one of
$L1_{0}$
-FePt/Fe for all the soft layer thicknesses.