Improved exchange bias of PtCr antiferromagnets with FeMn or Mn addition

In order to enhance the exchange coupling between antiferromagnetic PtCr and ferromagnetic CoFe based films, we have intentionally inserted FeMn or Mn at the interface but also throughout the volume part of the PtCr layer. Most differently from those studies with nonmagnetic impurities, the FeMn or Mn additive can largely increase the pinning field. These investigations reveal that Mn is the superior additive for this system. Especially, the small Mn concentration at the interface significantly improves the pinning field even by a factor of 4 while does not degrade the super thermal stability of PtCr. The strong dependence of exchange bias on the insertion layer will be argued to have its origin in increasing the moments of interfacial antiferromagnetic spins, and consequently, contribute to improve the pinning field.