The influence of 200 keV Ar-ion irradiation on the interlayer coupling in Fe/Cr multilayers exhibiting the giant magnetoresistance effect (GMR) is studied by the conversion electron Mössbauer spectroscopy (CEMS), magnetic hysteresis loops, magnetoresistivity and electric resistivity measurements and supplemented by the small angle X-ray diffraction (SAXRD).
An increase of interface roughness of Fe/Cr multilayers caused by irradiation with 200 keV Ar ions and doses exceeding 5x10¹² Ar/cm² is clearly seen in CEMS measurements, while, the SAXRD technique, even at higher ion doses, hardly detects such changes in microstructure. On the other hand, a subtle modification of the microstructure induces distinct changes in magnetization reversal (increase of the remanence magnetization) and strongly decreases GMR effect with increasing irradiation dose. The most prominent changes are observed for the samples with a small thickness of Cr layers.
The increasing immunity of GMR effect to ion irradiation with increasing thickness of Cr layers as well as correlation between changes in GMR and antiferromagneticaly coupled fraction suggest that the main effect responsible for the decrease of GMR is caused by the pinholes creation. Characteristic changes in the temperature dependence of the remanence magnetization measured for the as-deposited and irradiated samples results from an increase of pinholes density and their sizes during irradiation process.
This project was financially supported by Polish Committee for Scientific Research (KBN), grant number: PBZ/KBN-013/T08/23