Reversing exchange fields in CoFe/PtMn and CoFe/IrMn bilayers by carbon field irradiation

C-ion irradiation was performed in CoFe/PtMn and CoFe/IrMn systems with an applied field during irradiation to investigate the effects of the energy transfer between C ions and antiferromagnetic atoms (AF) on the exchange field H-ex. The irradiated CoFe/PtMn samples showed reduced exchange fields and coercivity, which was attributed to the lattice distortion of PtMn. When samples were irradiated with an applied field antiparallel to the original exchange-bias direction, a partially reversed H-ex was found in CoFe/PtMn, while a fully reversed H-ex in CoFe/IrMn was observed at the dose of 2x10(14) ions/cm(2). Rapid energy transfer and temperature increase, originating from the interaction between C ions and AF atoms, resulted in spin reversal and formation of reversed AF domains when samples were irradiated in antiparallel fields. In addition, the thermal relaxation of H-ex in CoFe/IrMn was suppressed by ion irradiation. (C) 2003 American Institute of Physics.