Cr90Ru10/Fe55Pt45及Cr90Ru10/Fe55Pt45/Cr90Ru10薄膜之磁性質及顯微結構研究

Abstract

本研究以直流磁控濺鍍的方式鍍製Cr90Ru10底層於表面自然氧化的矽基板上，並採用具有高結晶異向性常數之Fe55Pt45薄膜為磁性記錄層，以形成Cr90Ru10/Fe55Pt45及Cr90Ru10/Fe55Pt45/Cr90Ru10多層膜結構。探討Cr90Ru10底層、Cr90Ru10頂層及製程參數對Cr90Ru10/Fe55Pt45及Cr90Ru10/Fe55Pt45/Cr90Ru10多層膜之顯微結構、磁性質及其易磁化軸[001]方向之影響。 關於Cr90Ru10底層的製作，從XRD與TEM的分析顯示，我們發現可藉由濺鍍功率與基板溫度的改變，而獲得（002）平面平行膜面之從優取向的Cr90Ru10底層。在濺鍍功率固定為50W，基板溫度300℃至450℃時，Cr90Ru10底層有較佳的（002）平行膜面之從優取向。 我們發現Cr90Ru10（35 nm）/Fe55Pt45（25 nm）雙層薄膜的磁性質會隨著Fe55Pt45磁性層濺鍍功率改變而產生變化。在350℃的基板溫度下，濺鍍功率為10W至20W時，薄膜的平行膜面頑磁力Hc//可達2000 Oe以上。然而當濺鍍功率超過30W時，薄膜的Hc//大幅下降至1500 Oe以下。 基板溫度為350℃時，Cr90Ru10（35 nm）/Fe55Pt45（15nm）之Hc//為1815 Oe。當Fe55Pt45磁性層厚度增加到40 nm時，Hc//提升到3219 Oe。Cr90Ru10（35 nm）/Fe55Pt45（40 nm）雙層薄膜的Hc//為3219 Oe、平行膜面殘留磁化量Mr//為675 emu/cm3、平行膜面角形比S//約為0.91、Fe55Pt45磁性層的平均晶粒尺寸約為11 nm，具有應用於高密度水平磁記錄媒體的潛力。 我們發現在基板溫度300℃時，鍍製Cr90Ru10（15 nm）/Fe55Pt45（25 nm）雙層薄膜，薄膜的Hc//可達1509 Oe，顯示薄膜在此溫度下已發生序化。再將基板溫度提高到325℃，則Hc//上升到2247 Oe，Mr//為671 emu/cm3，S//=0.90，平均晶粒尺寸為7.91 nm。 當Cr90Ru10底層厚度在10 nm至100 nm之間，基板溫度為350℃時，薄膜的Hc//會隨著Cr90Ru10底層厚度的增加而提高。Cr90Ru10（15nm）/Fe55Pt45（25 nm）雙層薄膜的Hc//為2131 Oe。當Cr90Ru10底層厚度達50 nm時，Cr90Ru10（50 nm）/ Fe55Pt45（25 nm）雙層薄膜的Hc// 為 4000 Oe，平均晶粒尺寸約為10.67 nm。但是當底層厚度大於50 nm以後，Hc//趨向飽和，增加幅度較小。 在基板溫度350℃時，Cr90Ru10（15nm）/Fe55Pt45（25 nm）雙層薄膜的平均晶粒尺寸為8.60 nm，其Hc//為2131 Oe。Cr90Ru10（4 nm）頂層的加入會使FePt薄膜的平均晶粒尺寸下降，並有利於Hc//的提昇，其中Cr90Ru10（15nm）/Fe55Pt45（25 nm）/Cr90Ru10（4 nm）三層薄膜的平均晶粒尺寸為7.65 nm，Hc//為2300 Oe。

Cr90Ru10 underlayer is deposited on natural-oxidized Si substrate by dc magnetron sputtering, then deposits high magnetocrystalline anisotropy Fe55Pt45 films as magnetic layer on the Cr90Ru10 underlayer. A Cr90Ru10 top layer is deposited on the Fe55Pt45 layer. The effects of Cr90Ru10 underlayer, Cr90Ru10 top layer and process parameters on the microstructure, magnetic properties, and easy axis of Cr90Ru10/Fe55Pt45 and Cr90Ru10/Fe55Pt45 /Cr90Ru10 multilayer films are investigated. X-ray diffraction pattern and TEM analyses indicate that the (002) preferred orientation of Cr90Ru10 underlayer can be promoted by varying substrate temperature and sputtering power. Cr90Ru10（002） preferred orientation can be achieved by using dc power of 50W with substrate temperatures in the range of 300℃ to 450℃. Magnetic properties of the Cr90Ru10（35 nm）/Fe55Pt45（25 nm） bilayer films varie with sputtering power of Fe55Pt45 magnetic layer. When the substrate temperature is fixed at 350℃ and sputtering power was set in the range of 10 to 20W, the in-plane coercivity Hc// of Cr90Ru10（35 nm）/Fe55Pt45（25 nm） bilayer films is above 2000 Oe. However, the Hc// of Cr90Ru10（35 nm）/Fe55Pt45（25 nm） bilayer films is lower than 1500 Oe as the sputtering power is higher than 30W. As the substrate temperature is fixed at 350℃, the Hc// of Cr90Ru10（35 nm）/Fe55Pt45（15 nm） bilayer film is 1815 Oe. As the FePt magnetic layer thickness increases to 40 nm, the Hc// increases to 3219 Oe. Average grain size of the Fe55Pt45 magnetic layer in the Cr90Ru10（35 nm）/Fe55Pt45（40 nm） bilayer film is about 11 nm. Its in-plane remnant magnetization M// is 675 emu/cm3, and in-plane squareness S// is about 0.91. It has revealed its prominent potential to be applied as longitudinal magnetic recording media for high-density recording. An in-situ ordered Fe55Pt45 film in the Cr90Ru10（15 nm）/Fe55Pt45（25 nm） bilayer film is obtained at the substrate temperature of 300℃ and its Hc// is 1509Oe. When the substrate temperature increases to 325℃, the Hc// of Cr90Ru10（15 nm）/Fe55Pt45（25 nm） bilayer film is increased to 2247 Oe. Average grain size of the Fe55Pt45 magnetic layer in this film is about 7.91 nm. Its M// is 671 emu/cm3, and S// is about 0.90. When the thickness of Cr90Ru10 underlayer is in the range of 10-100 nm, the Hc// of the Cr90Ru10/Fe55Pt45（25 nm） bilayer film increases with increasing Cr90Ru10 thickness as the substrate temperature is 350℃. The Hc// of Cr90Ru10（15 nm）/Fe55Pt45（25 nm） bilayer film is 2131 Oe. As the Cr90Ru10 thickness increases to 50 nm, the Hc// increases to 4000 Oe. Average grain size of the Fe55Pt45 magnetic layer in the Cr90Ru10（50 nm）/Fe55Pt45（40 nm）bilayer film is about 10.67 nm. Average grain size of the Cr90Ru10（15 nm）/Fe55Pt45（25 nm） bilayer film is about 8.60 nm and its Hc// is 2131 Oe. After introducing 4 nm Cr90Ru10 top layer, the Hc// of Cr90Ru10（15 nm）/Fe55Pt45（25 nm）/Cr90Ru10（4 nm）multilayer increases to 2300 Oe and its average grain size is reduced to 7.65 nm. The addition of 4 nm Cr90Ru10 top layer on the Cr90Ru10（15 nm）/Fe55Pt45（25 nm）bilayer films increases Hc// and reduces the average grain size of Fe55Pt45 magnetic layer.