L10-FePt奈米線陣列之垂直磁性自旋閥

Abstract

本研究利用孔洞為50 nm之陽極氧化鋁(AAO)作為模板，再以電化學沉積之方式合成出FePt奈米線陣列。藉由X光繞射儀(XRD)觀察FePt奈米線陣列於700oC與5% H2/N2之環境下進行熱退火時FePt奈米線陣列將從無序相之面心立方晶格fcc轉換為有序L10相，FePt奈米線陣列於有序相L10相其矯頑磁場約為7.5 kOe，利用熱退火之方式，使L10相FePt奈米線陣列至（001）方向之磁化易軸。而L10相FePt奈米線陣列之矯頑磁場遠大於Ni3Fe，故FePt/Cu/Ni3Fe奈米線陣列中之FePt固定層與Ni3Fe自由層之磁性差異性，即形成具功能性之開關元件。藉由此性質合成FePt/Cu/Ni3Fe與FePt/NiO/Ni3Fe多層結構之奈米線，即可觀察巨磁阻(GMR)之現象與垂直式磁性自旋閥效應，而多層L10-FePt奈米線陣列其特性可被應用於一維磁性奈米材料。

FePt nanowires arrays were successfully prepared by electrodeposition into porous anodized aluminum oxide (AAO) templates with pore diameters of approximately 50 nm from a very simple electrolyte. The phase transition of FePt nanowire was from a disorder alloy distribution of fcc to ordered L10 phase after annealing at 700oC in 5% H2/N2, and it was observed by x-ray diffraction approach. FePt nanowires with L10 phase exhibit a large coercivity of 7.5 kOe. Thermal treatment was applied to obtain L10-FePt nanowires with (001) preferential orientation. The coercivity of L10- FePt nanowires is greater than that of Ni3Fe, therefore FePt/Cu/Ni3Fe nanowires exhibited a well-separated switching of the FePt fixed layer and the Ni3Fe free layer. This characteristic can be used to fabricate multi-segment of FePt/Cu/Ni3Fe and FePt/NiO/Ni3Fe nanowires which also can observed the giant magnetoresistance (GMR) and perpendicular magnetic spin valve effect. multi-segment of L10-FePt nanowires prepared by the present process have great potential for one dimension nanomagnetism application.