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.
Bibliographical noteFunding Information:
This work was supported in part by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (No. KRF-2006-331-D00230). FIG. 1. The MR curves of the as-deposited (black line), the field-annealed (red line), and the H-ion irradiated (blue line) IrMn-based spin valve. The H-ion irradiation dose was 2.8 × 10 18 ions ∕ cm 2 , which took 20 min at 550 eV . FIG. 2. Out-of-plane XRD spectra near (222) diffraction peaks of IrMn, Cu, CoFe, and NiFe measured at high angles for the three types of spin valves. Each layer was identified by curve fitting (not shown). FIG. 3. (a) XRD patterns printed on a two-dimensional image plate and (b) the enlarged image of out-of-plane XRD patterns for the H-ion irradiated spin valve. FIG. 4. Summary plots of IrMn (111) χ -rocking width (closed circles) and exchange bias (closed squares) of the as-deposited, field-annealed, and irradiated spin valves.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)