Ru underlayers for enhancement of in-plane magnetic anisotropy field of Ru/FeCoB film

FeCoB layer prepared on Ru underlayer exhibited a high magnetic anisotropy field Hk around 500 Oe. Sputtering conditions to fabricate Ru/FeCoB bilayered film with high Hk were examined. Low Ar gas pressure condition around 1 mTorr for the deposition of FeCoB layer was required to induce compressive stress in the film which may cause an expansion of the lattice. The sputtering gas of Ar was preferable than Kr to cause the lattice expansion which resulted in higher Hk. Thinner Ru underlayer caused high Hk of the Ru/FeCoB bilayered film. The sputtering gas pressure for Ru underlayer of 6 mTorr was better than that of 16 mTorr to attain high Hk of FeCoB upperlayer.