Exchange Coupling in Ferromagnet/Antiferromagnet Bilayers with ComparableTCandTN

Exchange coupling has been observed in FM/AF bilayers with $T_C$ close to, and less than, $T_N$. The exchange field $H_E$ and coercivity $H_c$ show an unusual temperature dependence due to the ${1/M}_F$ dependence and the influence of the FM ordering by the AF layer at $T>\mathrm{}{T}_C$. The exchange coupling energy vanishes at $T_N$, whereas the intrinsic $H_c$ vanishes at $T_C$. The FM/AF exchange coupling preserves some degree of ordering in the FM layer even at $T>\mathrm{}{T}_C$.