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標題: 二次退火對FePt(FeOx)及FePtX(X=Cu,C)複合薄膜之微結構與磁性質影響
Effects of two-steps annealing on microstructure and magnetic properties of FePt(FeOx) and FePtX(X=Cu,C) composite films
作者: 陳柏仁
Po-Ran Chen
關鍵字: 二次退火
two-steps annealing
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摘要: We used two steps annealing to form films with great perpendicular magnetization that could not make with multilayers or co-sputter. The two steps annealing tuned composition of films as a result of enhanced atomic diffusion. The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, we flowed 0~10 vol.% oxygen and deposited FeOx(3 nm)/Fe(3 nm)/L10FePt(11 nm) trilayer with plasma oxidation. Two-step magnetic hysteresis loops were found in trilayer that suggested the magnetization reverse of FeOx and Fe/L10FePt were not at the same time. The trilayers were annealed again at 500℃ and 800℃ for 3 minutes. When trilayers were annealed at 500℃, the magnetization reverse was coupled with single switching field and the layer structure changed to FeOx/FePt bilayer due to oxygen diffusion. The out-of-plane coercivity of single FePt was changed from 15.3 kOe to 10.4 kOe for FeOx/FePt bilayer. But further annealed at 800℃, the hysteresis loops presented soft-magnetic loop due to the oxygen was diffused into FePt layer and disordered the L10 phase. In summary, two steps annealing can controll the oxygen diffusion and tune the coupling between soft-magnetic and hard-magnetic layer. In second part, we investigated the C added in FePt layer in order to suppress the grain growth with two step annealing. Multilayers FePt(1 nm)/[Cu(x nm)/Fe(1 nm)]5/C(1 nm)/L10FePt(11 nm) were alternately deposited on a glass substrate, in order to reduce Curie temperture(Tc). The residual magnetization of hard axis was increased by C additive(to 400~500 emu/cm3) but decreased with Cu interleaved(to ~250 emu/cm3). We suggested with the magnetization of Fe arrayed with parallel to films. The specimen was annealed again at 200~600℃ for 3 minutes. The Mr of hard axis declined and Hc of easy axis elevated, and the tendency was promoted in Cu environment due to melting point of films were decreased. The film compositions can be tune with further annealed, the proportion of Fe and Pt change from 52 : 48 to 59.8 : 40.2 due to atomic duffusion. In summary, two step annealing can tune composition of films that improve properties of the films and maintain anisotropy.
此實驗為了製備以多層膜或共鍍方式無法製作的FePt薄膜性值,故利用二次快速升溫退火的方式,讓膜層內部原子交互擴散以及調整膜層的成分,達到微調整體薄膜性質並保持良好之磁晶異向性。此實驗可以分成兩大部分:第一部分為在非晶玻璃基板上製備具良好垂直異向性之Fe(6 nm)/L10FePt(11 nm)薄膜,為了探討氧氣擴散對膜層耦合的影響,通入流量0~10%體積百分率之氧氣形成氧化電漿製備FeOx(3 nm)/Fe(3 nm)/L10FePt(11 nm)三層薄膜,而我們發現當氧氣通入會產生兩階段翻轉之磁滯曲線即FeOx與Fe/L10FePt之磁矩翻轉不一。將樣品進行500℃與800℃3分鐘二次快速退火,在二次退火500℃其氧氣擴散至Fe層形成FeOx(6 nm) /L10FePt(11 nm)之成分梯度薄膜,成功提升交互耦合效果並將垂直矯頑磁力由15.3 kOe(序化FePt)降至10.4kOe(3 vol.% O2),但將二次退火溫度提升至800℃,氧氣會擴散至FePt層破壞轉變為軟磁相FePt。總括可利用二次退火機制使氧氣擴散並提升硬磁層與軟磁層之交互耦合能力。 第二部分以添加C抑制二次退火造成晶粒成長之現象,並將厚度為0.2~1nm Cu與Fe交互穿插形成FePt(1)/[Cu(x)/Fe(1)]5/C(1 nm)/L10FePt(11 nm)複合薄膜,以Cu添加來降低整體膜層的居里溫度。而我們發現水平殘留磁化量會隨著C厚度增加而增加(400~500 emu/cm3)但隨Cu穿插而下降(~250 emu/cm3),此與Fe原子沉積時之排列方向有關,經二次快速退火200~600℃,其水平殘留磁化量隨溫度上升而下降且垂直矯頑磁場會增加,我們也發現此變化在有Cu穿插之樣品會在較低的二次退火溫度(400℃)發生,即在有Cu的環境下整體膜層之熔點下降進而提升擴散速率,而由成分量測也可以得知經二次快速退火其膜層成分會因原子擴散而改變,Fe與Pt之原子比例由原本的52 : 48轉變為59.8 : 40.2。由研究證實二次退火可利用原子擴散達到微調薄膜成分形成成分梯度薄膜或合金化,進而改善FePr基膜層之垂直異向性。
其他識別: U0005-2706201411542100
文章公開時間: 2017-07-03
Appears in Collections:材料科學與工程學系



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