摘要
我們以水熱合成法(hydrothermal synthesis)製備DyMn2O5奈米棒。經由高溫熱退火製備出不同尺寸與不同長寬比之樣品。並製做出了兩批一系列不同大小的樣品做為比較。同時再以固態反應法(conventional solid-state reaction)製備塊材樣品作為對照組。晶格結構與尺寸大小首先利用X-ray 跟 FE-TEM鑑定之。接著使用PPMS量測其磁性質。 由FE-TEM之照片統計，可以得出nanorods的尺寸分別為第一批：45(12) nm×19(3) nm、 48(12) nm×22(9) nm、 54(9) nm×25(4) nm、84(26) nm×36(9) nm、以及 213(84) nm×111(22) nm，以及第二批:、40(9) nm×24(6)、41(9) nm×24(4) nm、50(10) nm×24(6) nm。選區電子繞射實驗顯示其奈米棒長軸沿著c軸成長。其中40(9) nm×24(6)、45(12) nm×19(3) nm、 48(12) nm×22(9) nm 之奈米棒在38 K到43 K觀察到與塊材具有相同反鐵磁特徵的磁化率峰。推測有一磁臨界粒徑存在長軸等於48到50 nm之間。
並列摘要
Two series of DyMn2O5 nanorods were synthesized by hydrothermal method in different time. They have different length by long axis with different annealing temperature. X-ray diffraction revealed the crystal structures are formed as orthorhombic Pbam phase for each sample. SAED results show that the long side of nanorods is parallel to c axis for all three samples. Magnetic ac susceptibility measurements were used to determinate magnetic properties. Curie-Weiss law is employed to analysis the ac magnetic susceptibility curves. It is found that Néel temperature is increased with increasing length. Antiferromagnetic peaks at around 38 and 43 K were only observed as length longer than 46 nm, which implied a critical length of magnetic ordering at around 50 nm.
參考文獻
延伸閱讀
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