磁性材料的電阻率會隨著磁場與電流的夾角不同而改變；例如在鐵、鈷、鎳等純元素金屬中，磁場平行於電流方向時其電阻會大於磁場垂直於電流方向的電阻，此效應稱為異向性磁阻(Anisotropy Magnetoresistance, AMR)；當材料是薄膜形式時，在磁場垂直於電流方向部分，又可以分為垂直於膜面(Perpendicular)以及平行於膜面(Transverse)兩種，因為幾何尺寸效應，平行於膜面的電阻率會大於垂直於膜面的電阻率。近幾年的研究中，曾經在釔鐵石榴石(yttrium iron garnet, YIG)上長Pt發現了縱向電阻率與垂直於膜面電阻率大於平行於膜面電阻率( )的現象，與以往的異向性磁阻現象不同。為了解釋這樣的現象，有兩種不同的方式被提出：其一是因為Pt很接近Stoner準則，因此Pt會被誘導出磁性，而Pt層的磁阻貢獻便會產生這樣的現象，稱之為混合式磁阻(Hybrid MR)或是磁鄰近效應磁阻(Proximity MR)，而另一種理論則是認為因為Pt會因為自旋霍爾效應產生自旋流，自旋流會因為磁性層的磁矩方向不同而在介面上穿透或反射，因此影響電阻率，這樣的行為稱為自旋霍爾效應磁阻(Spin Hall Magnetoresistance)。我們實驗室過去發現了在Pt/Ni以及Pd/Ni的多層膜結構中，有 的異常現象，在此研究中確認此現象必須在Ni層夠薄，以及Pd夠厚的情形才會發生，並且此結果跟溫度是相關的；此外將樣品退火過後也發生了異常 的行為，當材料改變為Ta/Ni作為對照組時，行為與傳統異向性磁阻一致；根據數據，這些異常的結果，是同時跟自旋霍爾效應磁阻以及磁鄰近效應磁阻有關的。

Metallic ferromagnetic materials exhibit anisotropic magnetoresistance (AMR) effect. For Fe, Co, and Ni, the resistivity measured with current parallel to the applied magnetic field is larger than that with current perpendicular to the applied magnetic field. In thin-film forms, two configurations could be distinguished for current perpendicular to the applied field. One is field in the film plane (transverse MR, TMR), and the other is field perpendicular to the plane (perpendicular MR, PMR). In single-composition films, such as Co or Ni films, the effect of longitudinal ML (LMR) is larger than that of TMR, and then the effect of TMR is larger than that of PMR due to ‘Geometric Size Effect’. In recent researches, unusual resistivity in the Pt/yttrium iron garnet (YIG) structure has been reported. The resistivity in the Pt/YIG structure is in the sequence of . Two different theories were proposed to explain this result. The one called the Hybrid MR is that the Pt acquires induced magnetization by YIG layer. The other one called spin Hall MR is that the Pd layer generates spin currents by the spin Hall effect, and the spin current reflects or transmits according the magnetization direction in the YIG layer. In our previous studies, we found that in the Pd/Ni and Pt/Ni multilayer structure. In this study, we found that this result is both thickness and temperature dependent. According to our experiment data, we conclude that this result is associated with the Hybrid MR and the spin Hall magnetoresistance concurrently.

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