Giant Magnetoresistance in (CoxFe1-x/Cu)n Multilayers.

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Abstract
We report that giant magnetoresistance (MR) at room temperature up to 50% for low field of 0.9 kOe can be attained in (CoxFe1-x/Cu)n multilayers. A set of (CoxFe1-x/Cu)n multilayers was prepared by the ion beam sputter deposition method on MgO(110) single crystal substrates. All samples were confirmed to have hexagona1 structure of CoxFe1-x by X-ray diffraction measurements. The hexagonal c-axis is in the film plane, which induces in-plane uniaxial magnetic anisotropy of the order of 106 erg/cc. This anisotropy brings low saturation field in MR curves. We also investigated argon acceleration voltage (VB) dependence of the MR ratio, which is quite large and has a maximum around VB=600 V for [Co(10 Å) /Cu (10Å)]16 and [Co9Fe(10 Å)/Cu(10 Å)]16 multilayers. In the preparation condition of obtaining the maximum MR ratio, almost perfect antiferromagnetic coupling of the CoxFe1-x layers via thin Cu layes is realized. We found that the MR ratio of CoxFe1-x/Cu multilayers is larger than that of h/ Cu multilayers in the higher Co-concentration range of the CoxFe1-x alloy.