Influence of the Ar-ion irradiation on the giant magnetoresistance in Fe/Cr multilayers

Abstract

The influence of 200 keV Ar-ion irradiation on the interlayer coupling in Fe/Cr multilayers exhibiting the giant magnetoresistance (GMR) effect is studied by the conversion electron Mössbauer spectroscopy (CEMS), vibrating sample magnetometer hysteresis loops, magnetoresistivity, and electric resistivity measurements and supplemented by the small-angle x-ray diffraction. The increase of Ar-ion dose causes an increase of interface roughness, as evidenced by the increase of the Fe step sites detected by CEMS. The modification of microstructure induces changes in magnetization reversal indicating a gradual loss of antiferromagnetic (AF) coupling correlated with the degradation of the GMR effect. Distinctly weaker degradation of AF coupling and the GMR effect observed for irradiated samples with a thicker Cr layer thickness suggest that observed effects are caused by pinholes creation. The measurements of temperature dependence of remanence magnetization confirm increase of pinhole density and sizes during implantation. Other effects which can influence spin dependent contribution to the resistance, such as interface roughness as well as shortening of mean-free path of conduction electrons, are also discussed.

High-energy ion beam irradiation of Co/NiFe/Co/Cu multilayers: Effects on the structural, transport and magnetic properties

“…Moreover, 11 the nuclear energy loss at the present energy range is weakly sensitive to the projectile charge-state since the target is neutral, limiting the range of the potential. In that way, the present results, which are in fact very similar to the findings observed at lower irradiation energies such as with 200 keV Ar-ions in Fe/Cr MLs [47], indicate that the nuclear stopping power is probably responsible for a pinhole creation. …”

“…Ne experiments [46] and a factor of 6 for 200 keV Ar experiments [47]). However, the product of specific nuclear energy loss and fluence for the onset of magnetic effects in these low-energy experiments is about the same as in current experiments.…”

Mössbauer spectroscopy, interlayer coupling and magnetoresistance of irradiated Fe/Cr multilayers

“…However, for t Cr ≥ 0.7 nm, |J AF | initially slightly increases and then decreases. The increasing immunity of GMR and antiferromagnetic coupling to ion irradiation for the thicker Cr layers was also observed in our previous paper [8] and suggests that the main effect responsible for degradation of GMR is due to pinholes creation during irradiation.…”

“…In this contribution the preliminary experimental results presented in [8] are supplemented by the new ones. In particular, our investigations are extended to a new set of Fe/Cr multilayers with various thickness of Cr spacer and to wider range of Ar ion dose.…”

Modification of microstructure and magnetic properties of Fe/Cr multilayers caused by ion irradiation

“…Simultaneously irradiation leads to the gradual disappearance of linearity of M(H) dependence. We applied the procedure, proposed by Fullerton and Bader [15], of extracting the bilinear, J 1 , and the biquadratic, J 2 , terms of the exchange coupling from M(H) dependences. Fig.…”