[17p-501-1~7] 10.1 新物質・新機能創成（作製・評価技術）

▼ [17p-501-2] Mn-composition dependence of magnetoresistance ratio of Co₂MnSi-based giant magneto-resistance devices

〇(M2)井上 将希¹、Hu Bing¹、Moges Kidist¹、犬伏 和海²、中田 勝之²、山本 眞史¹、植村 哲也¹ (1.北大院情報、2.TDK)

キーワード：Spintronics, Heusler alloy, GMR

We have shown that harmful defects in Heusler alloy thin films of Co₂MnSi (CMS), Co₂(Mn,Fe)Si (CMFS), and Co₂MnGe can be suppressed by appropriately controlling the film composition, i.e., Co_Mn antisites detrimental to the half-metallicity can be suppressed by adding an excess Mn, and have demonstrated high tunneling magnetoresistance (TMR) ratios of up to 1995% (354%) at 4.2 K (290 K) in CMS/MgO/CMS MTJs having Mn-rich CMS electrodes, and up to 2611% (429%) at 4.2 K (290 K) in CMFS/MgO/CMFS MTJs having (Mn+Fe)-rich CMFS electrodes. The purpose of the present study was to clarify the influence of off-stoichiometry for CMS films on the MR ratio of GMR devices. To do this, we fabricated current-perpendicular-to-plane (CPP)-GMR devices having CMS electrodes with various Mn compositions, α, and an Ag spacer, and investigated the influence of α on the magnetoresistance (MR) characteristics. We demonstrated that MR ratios as a function of Mn composition, α. The MR ratios increased with increasing α from 9% for Mn-deficient α = 0.62 to 17% for Mn-rich α = 1.45. This result suggests the continuous increase in the spin polarization with increasing α from a Mn-deficient to a Mn-rich composition. Thus, it is demonstrated that the suppression of Co_Mn antisite by a Mn-rich composition is effective in CMS-based GMR devices as in MTJs.