本實驗利用直流磁控共同濺鍍的方式來製作碳化鐵(Fe3C)磁顆粒嵌在非晶質碳基底的磁性薄膜。在適當濺鍍條件下，可以得到只含單一相的碳化鐵(Fe3C)磁顆粒的非晶質碳膜。薄膜的成分比例是採用歐傑電子能譜(AES)來作分析。分別將只含單一相碳化鐵(Fe3C)磁顆粒的薄膜進行熱處理，熱處理溫度為250到600℃，而熱處理恆溫時間為30到90分鐘。並藉由高解析穿透電子顯微鏡(HRTEM)與擇區繞射圖譜來觀察樣品的微觀結構。經過熱處理溫度Ta>=250℃的樣品，其磁顆粒粒徑變大且結晶性也變好。從高解析穿透電子顯微鏡的影像可清楚看到屬於碳化鐵(Fe3C)相的晶面(001)及(100)。且樣品內的磁顆粒粒徑隨著熱處理溫度的增高與熱處理時間的延長而變大。在熱處理溫度Ta=550℃時可得到最大的磁顆粒粒徑(18 nm)。
針對不同含碳濃度(37 at. % ~ 85 at. %)的樣品，量測其磁化強度隨溫度的變化M (T) 以及磁化強度隨磁場的變化M (H)。磁化強度對溫度的關係M(T)，採用零磁場冷卻(zero field cooling)與磁場下冷卻(field cooling)兩種方式進行量測，外加磁場的大小為100Oe。由磁化強度對溫度的關係Mzfc(T)，可以得到磁化率隨溫度的變化Xzfc(T) 。根據Wolhfarth's的理論模型來作模擬計算，結果顯示只含單一相碳化鐵(Fe3C)磁顆粒的初鍍膜，其實驗數據和理論模擬計算的結果完全吻合，且磁顆粒呈現log-normal的分佈。當薄膜經過熱處理後，磁顆粒的分佈型式改變，成為混合normal及log-normal兩種函數的分佈。此外，樣品的飽和磁化強度與頑磁場可由磁化強度對磁場的關係M(H)得到。從實驗結果發現，初鍍膜皆為超順磁性(superparamagnetic)，在室溫的頑磁場為零。在濺鍍壓力為4 mtorr下製作的含碳濃度為72 at. %的樣品，經過溫度550℃(60分鐘)熱處理後，於室溫可得到最大的頑磁場為965Oe。
本論文還針對只含單一相碳化鐵(Fe3C)磁顆粒的初鍍膜及經過不同熱處理溫度後的薄膜，探討其電阻與磁阻的特性。實驗結果顯示只有初鍍及熱處理溫度為250℃和350℃時，樣品的電傳導方式是屬於穿遂(tunneling)傳輸機制。而熱處理溫度Ta = 350℃的樣品，在量測溫度Tm = 2 K時量測到的磁阻變化率高達23 %。

Magnetic thin films of Fe3C nanograins embedded in an amorphous carbon matrix were synthesized by using a dc magnetron co-sputtering technique. The films containing pure Fe3C grains could be obtained only in proper sputtering conditions. Films containing only grains of Fe3C phase were subjected to post deposition annealing at temperatures of 250 to 600℃for 30 to 90 min, respectively. Auger electron spectroscopy (AES) was used to determine the atomic concentration and its fluctuations. The microstructure and phases of grains were determined by high-resolution transmission electron microscopy (HRTEM) and selected area diffraction (SAD) patterns. Very good crystallinity appeared at Ta>=250℃. From the HRTEM image, lattice spacings of 6.7 A - corresponding to Fe3C (001) planes - and 4.3 A - corresponding to Fe3C (100) planes - were observed. Higher annealing temperature and larger annealing time caused an increase of grain size. The largest grain (18 nm) was obtained at Ta = 550℃.
Both temperature and field dependent magnetizations, M(T) and M(H), were measured for samples of various carbon concentrations ( from 37 at. % to 85 at. %). M(T) were measured in both conditions of zero field cooling and a field cooling at H = 100 Oe. Experimental results of Xzfc(T) , obtained from MZFC(T), of zero field cooling, were theoretically fitted by using Wolhfarth's model of non-interacting particles with log-normal distribution function of particle size. Only the films containing pure Fe3C grains are well fitted theoretically. Once the film was annealed, the grains were longer of single log-normal distribution but were of mixed log-normal and normal distributions. Blocking temperature, grain size, and dispersion of grain size distribution are obtained from fitting results. Saturation magnetization, and coercivity are obtained from the results of M(H) measurements. Films, as deposited, are superparamagnetic and show zero room temperature coercivity. The largest room temperature coercivity of 965 Oe is obtained for the sample of 72 at.% C made at the sputtering pressure of 4 mtorr and annealed at the temperature of 550℃ for 60 min.
The temperature-dependent resistance and the field-dependent magnetoresistance were measured for as-deposited films and films annealed at temperatures from 250 to 550℃for a period of 60 min. Results of temperature-dependent resistance show electrical tunneling conductance in as-deposited film and films annealed at Ta = 250 and 350℃only. The largest magnetoresistance ratio (MR) of 23 % at temperature Tm = 2 K was observed for Ta = 350℃. The variations of both the temperature dependence of resistance and the magnetoresistance with the annealing temperature are discussed.

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