釔錳氧化物奈米棒之磁性與結構研究

Studies of magnetic and structural properties of YMn2O5 nanorods

夏希琞(Hsi-Sheng Hsia)

指導教授 ： 楊仲準

中原大學/理學院/物理研究所/碩士(2016年)

https://doi.org/10.6840/cycu201600748

摘要

YMn2O5奈米棒透過水熱合成法合成，並用高溫爐加溫至400℃、500℃、600℃、700℃做熱退火處理，得到含原始溫度一共五種的熱退火樣品。透過X光粉末繞射鑑定樣品結構均為斜方晶系之pbam純相。透過掃描式電子顯微鏡影像分析統計得其樣品尺寸，分別對應熱退火溫度260℃、400℃、500℃、600℃、700℃之樣品大小，以短軸×長軸之方法依序標示為36(10) nm × 64(22) nm、30(8) nm × 54(19) nm、35(10) nm × 61(18) nm、36(10) nm × 71(32) nm、57(13) nm × 141(54) nm。利用高解析穿透式電子顯微鏡影像及選區電子繞射影像得知樣品皆沿晶軸c軸方向成長，因此定義奈米棒長軸長度為，但由於熱退火溫度與熱退火溫度TA = 700℃以下時，樣品大小並無辨別性，因此用熱退火溫度來辨別不同之樣品。磁化率實驗中，不同尺寸樣品在低溫下皆有明顯反鐵磁化峰，但於加場降溫升溫量測實驗中僅熱退火溫度TA = 700℃之樣品在溫度45 K下，磁化率有明顯上升。由磁滯曲線實驗得知樣品之矯頑力會隨著熱退火溫度升高而下降，說明樣品在熱退火溫度上升後，內部產生之缺陷結構隨之下降。變溫拉曼量測發現外加磁場可以有效降低樣品熱退火溫度TA = 500、700℃隨溫度變化之Ag及B1g之拉曼振盪模的扭曲及改變樣品因熱漲冷縮所造成的偏移，表示Ag及B1g之拉曼振盪模會受到外加磁場影響而改變，並意味著磁生交互作用存在。

關鍵字

稀土元素 ； 釔錳氧化物 ； 錳氧化合物 ； 奈米棒 ； 磁學 ； 磁性 ； 磁性材料 ； 多鐵材料 ； 鐵磁 ； X光粉末繞射 ； 晶體結構 ； 拉曼光譜

並列摘要

Multiferroic YMn2O5 nanorods were synthesized by hydrothermal process. The samples were annealed to temperatures 260℃ 400℃, 500℃, 600℃ and 700℃. The phase purity was verified by x-ray diffraction(XRD) and confirm as crystal in orthorhombic with space group Pbam. The particle sizes were calculated from the images of field emission scanning electric microscope(FE-SEM) and label in the from of long axis × short axis as 36(10) nm × 64(22) nm、30(8) nm × 54(19) nm、35(10) nm × 61(18) nm、36(10) nm × 71(32) nm、57(13) nm × 141(54) nm, respectively. The images of high resolution transmission electron microscope(HR-TEM) and selected area electron diffraction(SAED) shows the long axis are parallel to c axis of crystals as defined of . However, the axial lengths are unidentified when annealing temperature below 700℃, the annealing temperature were used to label and distinguish the samples. Antiferromagnetic peak is observed in all samples during susceptibility but only the sample with annealing temperature 700℃ increase significantly in susceptibility under temperature 45 K during the field cool(FC) process. In hysteresis loop, the coercivity decrease along with annealing temperature of the sample increase. This explain the defect of interior structure of the crystal is decreasing accompanied with increasing in annealing temperature. The exterior magnetic field was found to affect Ag and B1g mode in temperature dependent Raman spectrum which is correlated with exchange integral. The exchange integral could further expand to Mn-O-Mn bond angle and Mn-O bond length. This phenomenon also implies that there is magnon-phonon interaction inside the crystal.

並列關鍵字

Rare Earth ； Yttrium ； YMn2O5 ； RMn2O5 ； nanorods ； Magnetism ； Magnetic material ； multiferroic ； ferromagnetic ； XRD ； crystal structure ； Raman spectrum

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