【摘要】：低維納米材料是當前科學研究的熱點之一,低維納米材料包括二維、一維和零維納米材料。其中零維納米材料在材料結構上可以表現(xiàn)為量子點、納米島等。納米島是由有限數(shù)目的原子構成,在x-y平面及z方向上的尺寸均在納米量級,被譽為是“人造原子”。納米島與其它磁性材料相比可以顯著地提高比表面積,主要在磁儲備裝置、小結構高覆蓋率太陽能電池、鋰離子電池和光電探測器等有潛在的應用前景。因此,磁性納米島的理論研究對其應用有重要的指導意義。本文基于相關有效場理論研究了六角磁性納米島的物理特性。論文中,主要研究了各物理參數(shù)對磁性納米島的磁矩、磁化率、相變溫度、磁滯回線、階梯效應、內能、比熱的影響。結果顯示,改變交換耦合作用、磁晶各向異性和橫場時,系統(tǒng)會出現(xiàn)重入現(xiàn)象,并且在一定參數(shù)范圍內,系統(tǒng)會同時出現(xiàn)兩個相變點和一個補償點;隨著各參數(shù)的變化,系統(tǒng)內能曲線會在不同的位置出現(xiàn)拐點,即相變溫度不同;比熱曲線在相變溫度處會出現(xiàn)奇異現(xiàn)象,這是典型的二級相變特點;當系統(tǒng)處于低溫時,在外場的作用下,磁矩表現(xiàn)出明顯的階梯效應,表面交換作用和磁晶各向異性對階梯效應有重要影響;交換耦合作用、磁晶各向異性、橫場及溫度都會影響系統(tǒng)磁滯回線的環(huán)數(shù)及形狀�；谙嚓P有效場理論還研究了立方結構磁性納米島的物理特性。立方結構納米島的磁矩、相變溫度及階梯效應受核的磁晶各向異性影響較大。與六角結構納米島的變化規(guī)律類似,在一定的參數(shù)范圍內,系統(tǒng)也出現(xiàn)了多個相變點。內能、比熱曲線的變化趨勢與六角結構納米島相似。在低溫時,系統(tǒng)出現(xiàn)了磁矩階梯和多環(huán)的磁滯回線。
[Abstract]:Low-dimensional nanomaterials, including two-dimensional, one-dimensional and zero-dimensional nanomaterials, are one of the hot spots in scientific research. The structure of zero-dimensional nano-materials can be represented as quantum dots, nano-islands and so on. The nano-island is composed of finite number of atoms. The size of the nano-island is in the order of nano-scale in the plane and z-direction. It is known as "man-made atom". Compared with other magnetic materials, nano-islands can significantly increase the specific surface area, mainly in magnetic storage devices, small structure and high coverage solar cells, lithium-ion batteries and photodetectors and other potential applications. Therefore, the theoretical study of magnetic nanisland has important guiding significance for its application. In this paper, the physical properties of hexagonal magnetic nanisland are studied based on the correlation effective field theory. In this paper, the effects of physical parameters on magnetic moment, susceptibility, phase transition temperature, hysteresis loop, ladder effect, internal energy and specific heat of magnetic nanisland are studied. The results show that when the exchange coupling is changed, the magnetocrystalline anisotropy and transverse field will occur, and there will be two phase transition points and one compensation point at the same time in a certain parameter range. With the change of each parameter, the inflexion point will appear in different positions, that is, the phase transition temperature is different, and the specific heat curve will appear strange phenomenon at the phase transition temperature, which is a typical second-order phase transition characteristic. When the system is in low temperature, the magnetic moment shows obvious ladder effect under the action of external field, and the surface exchange action and magnetocrystalline anisotropy have an important influence on the ladder effect. Exchange coupling, magnetocrystalline anisotropy, transverse field and temperature all affect the number and shape of hysteresis loops. Based on the correlation effective field theory, the physical properties of cubic magnetic nanisland are also studied. The magnetic moment, phase transition temperature and ladder effect of the cubic island are greatly affected by the magnetocrystalline anisotropy of the nucleus. Similar to that of the hexagonal structure, there are many phase transition points in the system within a certain range of parameters. The variation trend of internal energy and specific heat curve is similar to that of hexagonal structure nano-island. At low temperature, magnetic moment ladder and multi-loop hysteresis loop appear in the system.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB383.1

【參考文獻】

中國期刊全文數(shù)據(jù)庫 前3條

1 馮麗雅;辛子華;王吳韜;;一維鉆石鏈反鐵磁Ising模型磁化的模擬[J];計算物理;2010年04期

2 楊秀會;;W(110)基底上的鐵納米島初始自發(fā)磁化態(tài)的微磁學模擬[J];物理學報;2008年11期

3 羅亮;伊福廷;張菊芳;;氯化銫納米島生長技術[J];功能材料與器件學報;2008年01期

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本文編號：2444229