【公開日：2024.07.25】【最終更新日：2024.06.22】

課題データ / Project Data

課題番号 / Project Issue Number

23NU0260

利用課題名 / Title

Development of 3D magnetic memory

利用した実施機関 / Support Institute

名古屋大学 / Nagoya Univ.

機関外・機関内の利用 / External or Internal Use

外部利用/External Use

技術領域 / Technology Area

【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-

【重要技術領域 / Important Technology Area】（主 / Main）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials

キーワード / Keywords

Magnetic memory, Nanowires, Atomic Force Microscope,走査プローブ顕微鏡/ Scanning probe microscope,ナノワイヤー・ナノファイバー/ Nanowire/nanofiber

利用者と利用形態 / User and Support Type

利用者名（課題申請者）/ User Name (Project Applicant)

HASAN Md Mahmudul

所属名 / Affiliation

早稲田大学

共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes

ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes

Daiki Oshima

利用形態 / Support Type

（主 / Main）共同研究/Joint Research（副 / Sub）-

利用した主な設備 / Equipment Used in This Project

NU-204：原子間力顕微鏡

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

Multilayered magnetic nanowires are important for next-generation magnetic storage systems. Employing current-induced domain wall (DW) motion in magnetic nanowires may provide a non-volatile memory system that surpasses conventional magnetic hard disc drive storage in terms of performance and robustness. Racetrack memory devices, for instance, use an electrical current applied in the nanowires to move the DWs along nanowires while storing digital bits as the magnetization direction of magnetic domains separated by a DW. Several DW can be stored in a tiny area on a ferromagnetic wire which offers an extraordinarily high storage density compared to traditional magnetic memories. To accurately and consistently determine the location of the magnetic domain and domain wall, magnetic nanowires need to have a multilayered structure with modified magnetic characteristics. CoPt materials are well-suited for magnetic memory and have been extensively researched as high-density recording medium because of their significant magnetic anisotropy. CoPt multilayered alloy nanowires were produced by an electrodeposition process using a polycarbonate template membrane (PT). When the potential was changed to alter the composition of the CoPt alloy, nanowires were prepared by filling the 100 nm-diameter PT nanoholes with a multilayered CoPt alloy. The resulting CoPt multilayered nanowires have a relative chemical composition of [Co₈₀Pt₂₀/Co₃₀Pt₇₀]n and a periodic structure resembling bamboo.  Additionally, a single Co-rich alloy nanowire with a relative composition of Co₈₀Pt₂₀ was prepared, displaying ferromagnetic characteristics.

実験 / Experimental

The electric connection was made by covering one side of the PT with a thin layer of Cu (400 nm) using the spurring method. The electrodeposition solution consisted of 0.5 M H₃BO₃, 0.1 M CoSO₄.7H₂O, and 0.001 M Pt (NH₃)₂(NO₂)₂. The pH of the solution was 5.2 and the electrodeposition solution rotation speed was 200 rpm at 40^o C. Hokuto Denko electrochemical measuring equipment was used for the electrodeposition procedure. By employing -1000 mV versus Ag/AgCl (sat. KCl) as the reference electrode and Pt mesh counter electrode, single-layered Co-rich alloy (Co₈₀Pt₂₀) nanowires were created. The alternate Co-rich (Co₈₀Pt₂₀) and Pt-rich (Co₃₀Pt₇₀) alloys multilayered nanowires were prepared by applying -1000 mV and -100 mV versus Ag/AgCl (sat. KCl), respectively.

結果と考察 / Results and Discussion

The field emission scanning electron microscopy (FE-SEM) picture displayed the single-layered Co₈₀Pt₂₀ nanowires (27 μm) and multilayered [Co₈₀Pt₂₀/Co₃₀Pt₇₀]n nanowires (22 μm) having an average diameter of around 100 nm. Multilayered nanowires with dark and bright layers is due to the alternative CoPt alloy compositions. The thickness of each layer is around 100 nm. Both types of nanowires have no voids, making them ideal for storing applications. The ferromagnetic characteristics of Co-rich alloy (Co₈₀Pt₂₀) nanowires were assessed using AFM and MFM. The AFM picture displayed a long straight nanowire (Fig. 1c). The MFM picture was obtained without applying any magnetic field by scanning the sample at a lift height of approximately 50 nm above the surface to verify the nanowire's ferromagnetic characteristics . The Co-rich alloy nanowire exhibited magnetic contrast (Fig. 1d). This demonstrated that the Co-rich alloy nanowires have ferromagnetic characteristics. The ferromagnetic layer is required to construct a 3D multilayered magnetic memory device. Due to the complex domain structure that forms a multivortex structure at the end of the nanowire, MFM exhibits a complex contrast at its end.

図・表・数式 / Figures, Tables and Equations

Fig. 1. FE-SEM of (a) Co-rich alloy and (b) CoPt multilayered alloy nanowires. (c) AFM and (d) MFM observation of a Co-rich alloy nanowire.

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

・This work was supported by JST, CREST (Grant Number JPMJCR21C1), Japan.
・共同研究者：大島 大輝 助教（名古屋大学大学院工学研究科）

成果発表・成果利用 / Publication and Patents

論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)

1. Md. Mahmudul Hasan, Preparation and Characterization of High Aspect Ratio Electrodeposited CoPt Multilayered Magnetic Nanowires, 2023 IEEE International Magnetic Conference (INTERMAG), , 1-5(2023).
   DOI: 10.1109/INTERMAG50591.2023.10265078
   
2. Md. Mahmudul Hasan, Electrodeposited CoPt multilayered-nanowire for 3D memory device, 2023 IEEE International Magnetic Conference - Short Papers (INTERMAG Short Papers), , 1-2(2023).
   DOI: 10.1109/INTERMAGShortPapers58606.2023.10228236
   

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

特許 / Patents

特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件