Influence of gas adsorption at the interface on the exchange coupling field of Ni-Fe/25at%Ni-Mn/Ni-Fe films

The magnetoresistance (MR) ratio of spin valves can be improved by reducing the thickness of the nonmagnetic interlayer, such as Cu, due to not only reducing the shunt, but also increasing the probability of electrons scattered through the Cu. However, at small thickness, interlayer coupling between the free and pinned layer is increased, which makes it difficult to control the bias point. The minimum thickness of the interlayer Cu was thereby limited to around 3 nm. On the other hand, it is reported that the ferromagnetic interlayer coupling that arises from the film roughness can be reduced by controlling the residual gas inside the deposition chamber. The same effect can also be achieved by exposing the wafer into an oxygen gas atmosphere right after the deposition of the high conductive Cu interlayer. By this method the thickness of the interlayer Cu was reduced successfully from 3.0 to 2.0 nm without increasing the interlayer coupling. As a result, the MR ratio and dRsq was improved by 12% and 48%, and showed 10% and 1.82 Ω, respectively. Furthermore, by inserting a Cu backlayer to form a spin filter spin valve structure an antiferromagnetic interlayer coupling was also observed.

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Enhanced exchange anisotropy of Ni–Fe/Mn–Ni bilayers fabricated under the extremely clean sputtering process

Tsunoda

Uneyama

Suzuki

et al. 1999

Journal of Applied Physics

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In order to clarify the influence of the impurities in the sputtering atmosphere on the exchange anisotropy of ferromagnet/antiferromagnet bilayers, Ni–Fe/Mn–Ni films were prepared under different purities of the sputtering atmosphere by changing the base pressure from 10−11 Torr [extremely clean (XC) process] to 10−7 Torr [lower grade (LG) process]. The correlation between the exchange anisotropy and the microstructure of the films is discussed. As a result, we found that: (1) The exchange anisotropy was enhanced in the XC processed films comparing to the LG processed ones, especially when the thicknesses of both the ferromagnetic and antiferromagnetic layers were very thin. (2) The critical thicknesses of the antiferromagnetic layers were 110 and 150 Å for the XC and the LG processed films, respectively. (3) In the XC processed films, the fcc-[111] direction of the Ni–Fe grains were highly oriented perpendicularly to the film plane and an enlargement of antiferromagnetic grains was observed. We conclude that the enhancement of exchange anisotropy is caused by the enlargement of antiferromagnetic grains in the XC processed films.

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Influence of gas adsorption at the interface on the exchange coupling field of Ni-Fe/25at%Ni-Mn/Ni-Fe films

Cited by 10 publications

References 5 publications

Exchange bias

Exchange bias

Reduction of interlayer coupling in bottom synthetic spin valves through a gas exposure process

Enhanced exchange anisotropy of Ni–Fe/Mn–Ni bilayers fabricated under the extremely clean sputtering process

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