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    Title: 鐵、鈷、鎳、銅鎳合金與鉑、鈀多層膜的異向性界面磁阻研究
    Study of Anisotropic Interface Magnetoresistance of Fe, Co, Ni, CuNi and Pt, Pd Combination Multilayered System
    Authors: 張哲鈞
    Chang, Che Chun
    Contributors: 李尚凡
    Lee, Shang Fan
    張哲鈞
    Chang, Che Chun
    Keywords: 異向性磁阻
    幾何尺寸效應
    異向性界面磁阻
    Anisotropic Magnetoresistance
    Geometric Size Effect
    Anisotropic Interface Magnetoresistance
    Date: 2012
    Issue Date: 2013-09-02 16:56:45 (UTC+8)
    Abstract: 異向性磁阻(Anisotropic Magnetoresistance, AMR)效應是指在磁性材料中的電阻率,當磁場平行於電流時會大於磁場垂直於電流時的值(ρH‖I > ρH⊥I)。而在薄膜材料中,磁場垂直於電流的電阻率又可以分為磁場方向平行於膜面(ρ⊥HIP)和磁場方向垂直於膜面 (ρ⊥HPP)。有趣的地方是這兩者的大小在單層膜與多層膜呈現了不一樣的行為。在Co、Ni的單層膜中ρ⊥HIP > ρ⊥HPP,此現象稱為幾何尺寸效應(Geometric Size Effect, GSE),但是在Co/Pt的多層膜中ρ⊥HPP > ρ⊥HIP,與Co的單層膜結果相反,此現象稱為異向性界面磁阻(Anisotropic Interface Magnetoresistance, AIMR),發生的物理原因至今並不清楚。
    本論文主要探討磁性多層膜的異向性界面磁阻的變化,樣品多層膜皆為磁性層與非磁性層交錯而成,磁性層材料為鐵(Fe)、鈷(Co)、鎳(Ni)以及弱磁性的銅鎳合金(CuNi),非磁性層的材料則選用最為接近滿足Stoner 準則(Stoner criterion)的鉑(Pt)和鈀(Pd),希望能夠釐清其發生的機制。由於目前認為異向性界面磁阻是界面(interface)造成的,所以樣品皆固定總厚度為200 nm,藉由改變交錯的層數來改變磁性層與非磁性層的界面數目,分析界面數目對異向性界面磁阻的影響。首先以XRD確認樣品的膜厚與品質,接著在10 K和300 K的溫度量測磁阻與角度的關係,所有樣品中都可以看到異向性界面磁阻(AIMR)的現象,而且所有樣品異向性界面磁阻的變化大致上都是隨著每層膜的膜厚越薄而增加。另外,在Ni/Pt、Ni/Pd和CuNi/Pd的多層膜中還看到了一個特殊的現象,就是磁場與膜面垂直的電阻(ρ⊥HPP)會大於磁場平行電流的電阻(ρH‖I),此現象與異向性磁阻(AMR)的趨勢相反,而且在此方向上旋轉的磁阻量測還有出現類似雙軸異向性(bi-axial anisotropy)的現象。在以SQUID量測的磁滯曲線中,看到飽和磁化量(Ms/cm3)和異向性場(anisotropy field, Hk)有隨著bilayers數目變多而增加的趨勢。
    Ferromagnetic metallic materials show anisotropic magnetoresistance (AMR) effect, that is the resistivity measured with current parallel to the applied magnetic field is larger than perpendicular to the applied magnetic field. In thin films with current in the plane, there are two directions for applying perpendicular magnetic field, one is field in plane, the other is field perpendicular to the plane. The magnetoresistance measured with three current-field relative directions were named longitudinal (L), transverse (T), and perpendicular (P) MR. In single ferromagnet Co and Ni films, the TMR is larger than PMR, which is named “Geometric Size Effect (GSE)”. However, in Co/Pt ferromagnet material/normal metal (FM/NM) multilayered systems, the behavior of PMR larger than TMR was observed and named “Anisotropic Interface Magnetoresistance (AIMR)” by Kobs et al. in 2011.
    In this thesis, we focus on the FM/NM multilayered systems and the influence of the interface in AMR effect. The FM and NM layers were Fe, Co, Ni, CuNi and Pt, Pd, Cu respectively. Both total thicknesses of FM and NM layers were fixed at 100 nm. We varied the numbers of FM/NM bilayer from 4 to 80. The XRD patterns were used to confirm the thickness and quality of our samples. In the MR measurements, the AIMR effect was observed in all samples, and the AIMR ratio increases when the interface number increases. An unusual behavior in Ni/Pt, Ni/Pd, CuNi/Pd, and Ni/Cu multilayers was observed, the perpendicular MR is larger than longitudinal MR. In addition, the anisotropic fields and saturation moments were measured by the SQUID. No apparent correlation between the unusual MR and magnetic properties was found.
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    Description: 碩士
    國立政治大學
    應用物理研究所
    100755010
    101
    Source URI: http://thesis.lib.nccu.edu.tw/record/#G0100755010
    Data Type: thesis
    Appears in Collections:[應用物理研究所 ] 學位論文

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