| 摘要: | 本文在探討兩種塊材化合物A0.1Mo2S2.9與SiMoS1+x (x≦1)，其各自擁有不同之晶格結構、電性與磁性。 A0.1Mo2S2.9樣品的XRD結果顯示，其中祇有Si0.1Mo2S2.9為單一的 Mo2S3結構，若摻雜物A為其它元素時，樣品都含有少量的Chevrel-phase雜相。 當摻雜的元素A為 碳、矽、鍺、硼與釕時，樣品具有抗磁性，其抗磁轉換溫度分別為4.08、4.23、3.82、4.62與4.35K， 而且在ρ-T圖上，可觀察到在相對應的溫度附近，其電阻率之斜率有明顯的變化，並且隨著磁場的增強而其電性轉折溫度也隨之降低。 在改變摻雜含量的實驗上，我們專注於擁有純相之SixMo2S3-x (x≦0.5)。其中Si0.33Mo2S2.67樣品的場冷(FC)及零場冷(ZFC)量測數據，顯示出在約63K時有類似鐵磁性的行為；而Si0.2Mo2S2.8 與 Si0.5Mo2S2.5 樣品的χ-T圖，則同時存在著二個不同溫度的抗磁轉換。
另外，塊材化合物SiMoS1+x (0≦x≦1)則為MoS2與合金Mo3Si3之混合物，但是在x=0.4時樣品卻成為MoS2與MoSi2之混合物。 SiMoS1+x (0≦x≦1)樣品的常溫電阻率，會隨硫含量的增加而明顯變大，當x = 0, 0.2, 0.8, 1時，樣品分別在4.25、4.41、3.32與3.75K有明顯的電性斜率變化，其中 x = 0與1時，樣品分別在4.54與3.51K有抗磁轉變。
In this thesis, the Mo2S3 doped with Si, C, B, and Ru, is identified to bear the same crystalline structure P21/m as that of Mo2S3 through XRD analysis. Diamagnetic transitions with χm ~ 10-4 emu/g-Oe at temperature ranging from 2K to 6K were observed in the doped samples of SixMo2S3-x (x = 0.1, 0.2, 0.33, 0.5). And both of the x = 0.2 and 0.5 samples were found to have double diamagnetic transitions with higher Tc at the same temperature of 6.01K. While SixMo2S3-x of x = 0.33 displayed an extra ferromagnetic-like response at 63K. The corresponding transition in resistivity of SixMo2S3-x with x = 0.1 was noticed to show a mild drop with less than 10% of its original transition values as measured down to 2K. But a superconducting-like magnetic field dependence on the phase transition of resistivity was also noted. Its diamagnetic signals were greatly reduced when the applied magnetic fields were raised to 103 Oes. In the doped samples of A0.1Mo2S2.9 (A = C, B, and Ru) the phase transition in resistivity at 4.08K, 4.62K, and 4.35K, respectively, exhibited similar fashion as that in the case of Si0.1Mo2S2.9.
For the other bulk samples SiMoS1+x (0≦x≦1), the polycrystalline structure reveals a poorly-crystalline MoS2 phase with several unknown reflections. In SiMoS1.4 all of the unknown reflections could be identified belong to alloy MoSi2 structure, but it is the only sample which doesn’t show diamagnetic transitions. While in the XRD of the rest samples most of the unknown reflections may be assigned to alloy Mo3Si3 structure. The electrical transitions in resistivity of bulk sample SiMoS1+x with x = 0, 0.2, 0.8, and 1, are observed at 4.25K, 4.41K, 3.32K, and 3.75K, respectively. And the samples with x = 0 and 1, reveal diamagnetic transitions at 4.54K and 3.51K, respectively. |
