Abstract
Ion irradiation has been used to manipulate the exchange field in the FeMn/NiFe system. Depending on the dosage and energy, the exchange field can be either enhanced due to defects acting as pinning sites or be suppressed to zero due to atomic intermixing. We recently reported that irradiated C ions in as-deposited NiMn films may result in modification of the phase transformation during the post-annealing process. In this article, the effects of the C ion dosage are investigated on phase transformation of PtMn and on GMR of PtMn-based spin valves.