Positive exchange bias in <i>as-deposited</i> ion-beam sputtered IrMn/CoFeB system

Abstract

The positive exchange bias (PEB) at room temperature in bottom pinned as-deposited IrMn(15 nm)/ CoFeB(10 nm) ion-beam sputtered bilayers is reported without any field cooling protocol. The necessary antiferromagnetic coupling of the interfacial spins and uniaxial exchange anisotropy in amorphous ferromagnetic CoFeB are caused by the energetic sputtered atoms that modify the local magnetic microstructure in situ. On magnetic annealing, enhancement in the coercivity and disappearance of PEB is observed due to the irreversible changes in the interfacial spin structure and CoFeB layer changing to ordered bcc (110).