SmMn2O5奈米尺寸效應與結構、磁性交互作用研究

Interplay between structure and magnetism and effect of size of SmMn2O5 nanorods

朱政洋(cheng-yang chu)

指導教授 ： 楊仲準

中原大學/理學院/物理研究所/碩士(2013年)

https://doi.org/10.6840/cycu201300712

摘要

本論文透過水熱法配合五種不同熱退火溫度300、500、700、900、1100 °C合成五種不同尺寸之SmMn2O5 之奈米棒。X光繞射實驗鑑定五組樣品之均為斜方晶系之Pbam純相。高解析度TEM影像與選區電子繞射分析顯示熱退火溫度300、500、700、900、1100 °C的樣品，依造短軸×長軸之方法標示，可分別寫為25(17) nm×58(42) nm、23(13) nm×75(36) nm、31(13) nm×88(34) nm、32(21) nm×92(73) nm、52(25) nm×126(53) nm。同時也發現所有樣品之長軸均沿著晶軸c軸成長。因此可以使用奈米棒的長軸(c軸方向長度)來定義成用以標示不同奈米棒樣品。
磁化率實驗發現樣品=58、88、92、126 nm之樣品分別在25、29、29.5、30 K出現一反鐵磁化率峰。這顯示了尺寸效應會弱化反鐵磁有序，並使之向低溫移動。而在2 K的磁滯曲線測試顯示了樣品有些微的磁滯現象。其矯頑力隨著增加而增大。
變溫拉曼光譜與x光繞射實驗均針對=92、126 nm之樣品做比較。實驗顯示=92 nm之樣品在150 K處有一些微的拉曼峰位移，而=126 nm之樣品，則在150 與250 K處有拉曼峰的位移。這正好與Mn-O之鍵長在同一溫度的熱漲冷縮斜率的改變相呼應
因此，尺寸效應造成在SmMn2O5在低溫下反鐵磁化率峰的弱化。而在磁相變溫度以上的高溫，則因為結構的扭曲，所以導致了拉曼峰的位移，並進而導致了不可忽略的自旋¬-軌道交互作用。

關鍵字

多鐵材料

並列摘要

Five sizes SmMn2O5 nanorods are fabricated by performing different annealing temperatures of 300、500、700、900、1100 °C. X-ray diffraction scheme is used to determinate the crystal structure and purity. All samples are form in orthorhombic Pbam phase. High-resolution TEM image and SAED pattern revealed the long and short axis of 300、500、700、900、1100 °C samples can be wrote in the form of long axis × short axis as 25(17) nm×58(42) nm、23(13) nm×75(36) nm、31(13) nm×88(34) nm、32(21) nm×92(73) nm、52(25) nm×126(53) nm. Furthermore, the long axis of all samples is growth along c axis, which can be used to label the sample name by the symbol .
Magnetic susceptibility experiments display an antiferromagnetic (AFM) peak is found in =58、88、92、126 nm samples at 25、29、29.5、30 K, respectively. This observation revealed the effect of size is majorly weaken the AFM ordering and shifted the peak to the lower temperature. The M-H curve shows a small hysteresis loopfor all samples. The coercivity are also increased with increasing .
Varied temperature Raman and x-ray diffraction are performed in =92、126 nm samples. A Raman peak shifted at 150 K in =92 nm sample. Similar peak shift are also found at 150 K and 250 K in =126 nm one. These observation echoes the observation of Mn-O at the same temperature ranges.
The effect of size of SmMn2O5 weak the AFM peak at low temperature. The structure distortion shifted the Raman peak and further results spin-orbit interaction above magnetic ordering temperature.

並列關鍵字

SmMn2O5

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