[20a-W241-1~12] 10.3 GMR・TMR・磁気記録技術

▲ [20a-W241-1] [Young Scientist Presentation Award Speech] L1₂ Ag-Mg ordered alloy spacer layer for Heusler alloy based current perpendicular-to-plane giant magnetoresistance devices

〇窪田 崇秀¹、伊奈 幸佑¹、温 振超¹、高梨 弘毅¹ (1.東北大金研)

キーワード：CPP-GMR,Heusler alloys

The current perpendicular-to-plane (CPP) giant magnetoresistive devices are attracting great interests for applying reading head elements for hard disk drives (HDDs) [1]. It was reported that the CPP giant magnetoresistive (GMR) devices using cobalt (Co) based Heusler alloy films and a silver (Ag) spacer layer exhibited larger change of the resistance area product (ΔRA) compared with that using the conventional 3d transition metal thin films [2, 3].However, it is still necessary to increase ΔRA values of CPP-GMR devices for the future HDD applications In this study, we have investigated Ag-Mg alloys for the spacer layer of the Heusler based CPP-GMR devices [4]. Tha stacking structure of the devices was as follow: MgO (100) substrate/Cr (20 nm) /Ag (40 nm) / Co2Fe0.4Mn0.6Si (CFMS, 20 nm) / Ag_100−xMg_x (5 nm) / CFMS(7 nm) / Ag (2 nm) / Au (5 nm). The Mg compositions, x of the Ag-Mg spacer layer were 0, 4, 8, 12, 17, 22, and 26 at.%. An epitaxial growth was confirmed for all the samples except for the one with x = 26 at.%. The L1₂ ordering of the Ag-Mg layer was also confirmed locally and widely for x = 17 and 22 at.%, respectively. MR ratio of the devices less depends on the Mg compositions. Maximum value of the MR ratio was 58% at room temperature for x = 22%. Here, MR ratio was defined as follows; MR ratio = (R_AP- R_P)=(R_P- R_para), where R_P(_AP),and R_para represent resistances at the parallel (anti-parallel) magnetization configuration and the parasitic resistance of the device electrodes. On the other hand, ΔRA increased with the Mg composition, up to x = 22at.%. The values of ΔRA were 17 and 20 mΩμm2 for x = 17 and 22 at.%, respectively, which were larger than that of the Ag spacer layer devices (13 mΩμm² These results indicate that the Ag-Mg alloy is good for enhancing the ΔRA value of the CPPGMR devices at the low RA region, which is suitable for HDDs applications.