Effects of H-ion irradiation on the properties of a spin valve

Irradiation with much less than 1.0 keV H ions significantly improved the properties of IrMn-based spin valves. The giant magnetoresistance (GMR) was increased from 8.1% to 9.6% and the exchange bias field from 355 to 565 Oe after irradiation at 550 eV. The irradiation achieved even higher GMR than that achieved by field annealing: 9.6% vs 8.7%. We attribute this enhancement to strong (111) textures of the IrMn antiferromagnet and CoFeCuCoFeNiFe layers, as well as to a narrow mosaic spread of the (111) IrMn, both of which were developed by momentum transferred during the ion bombardment. The irradiated spin valve showed exchange bias as large as and (111) textures as strong as those of the field-annealed spin valve. The significant difference in the GMR values of the irradiated versus the field-annealed spin valves was probably due to different degrees of intermixing between layers. In the case of irradiation, the low energy of the lightest H ion likely resulted in little intermixing and, hence, the interfaces were largely left intact, which kept the GMR values high.