【摘要】：隨著科學(xué)技術(shù)的發(fā)展,層狀磁性材料的研究與發(fā)展備受關(guān)注。其中,亞鐵磁材料中存在補(bǔ)償溫度,而補(bǔ)償溫度在磁記錄方面有著重要的應(yīng)用。同時(shí),合成薄膜材料的技術(shù)和手段多樣化,如脈沖激光沉積法、溶膠-凝膠法、金屬-有機(jī)物氣相沉積法、磁控濺射技術(shù)等,加上理論方面的突破與科學(xué)的實(shí)際運(yùn)用,磁性多層膜材料正進(jìn)入一個(gè)發(fā)展高潮期。針對(duì)層狀混自旋磁性材料,建立了亞鐵磁雙層混自旋(1/2,1)的Ising模型、亞鐵磁三層混自旋(1/2,1,3/2)的Ising模型和鐵磁三層混自旋(1/2,1,3/2)的Ising模型。利用Monte Carlo方法,系統(tǒng)地研究了亞鐵磁和鐵磁Ising系統(tǒng)的磁性質(zhì)和熱力學(xué)性質(zhì),分析和討論了溫度、交換耦合作用、薄膜層厚和磁性原子濃度對(duì)系統(tǒng)的磁矩、磁化率、內(nèi)能、比熱、補(bǔ)償行為和相變行為的影響。研究了亞鐵磁雙層混自旋(1/2,1)的Ising模型系統(tǒng)的交換耦合作用、層厚對(duì)系統(tǒng)磁性質(zhì)和熱力學(xué)性質(zhì)的影響。結(jié)果表明,層內(nèi)交換耦合Jbb增加時(shí),系統(tǒng)的相變溫度和補(bǔ)償溫度都在增加,發(fā)現(xiàn)Jbb越小,補(bǔ)償行為越容易出現(xiàn)。溫度與交換耦合作用的競(jìng)爭(zhēng),導(dǎo)致了磁矩曲線類型出現(xiàn)了Néel理論所預(yù)言的N型、Q型和P型曲線。層間交換耦合作用Jab的增加,對(duì)于相變溫度和補(bǔ)償溫度,幾乎沒有影響。隨著層厚L的增大,相變溫度先升高后不變,在L較小時(shí),補(bǔ)償溫度變化明顯。研究了亞鐵磁三層混自旋(1/2,1,3/2)的Ising模型系統(tǒng)的交換耦合作用、層厚和系統(tǒng)原子濃度對(duì)系統(tǒng)磁性質(zhì)和熱力學(xué)性質(zhì)的影響,重點(diǎn)研究了系統(tǒng)的補(bǔ)償行為和相變行為。研究結(jié)果表明:隨著Jbb的增加,補(bǔ)償溫度沒有影響,相變溫度增大。Jcc越大,補(bǔ)償溫度越難出現(xiàn)。隨著系統(tǒng)層厚L的增大,補(bǔ)償溫度不變,而相變溫度增加。子格層厚Lb增加,相變溫度增大,補(bǔ)償溫度消失,說明Lb越大,補(bǔ)償溫度越難出現(xiàn)。子格層厚Lc增加時(shí),相變溫度不變,補(bǔ)償溫度先增加后不變。改變系統(tǒng)原子濃度P,在相圖中發(fā)現(xiàn),系統(tǒng)出現(xiàn)了雙補(bǔ)償點(diǎn)。為了與相關(guān)有效場(chǎng)(EFT)的理論結(jié)果進(jìn)行比較,對(duì)鐵磁三層混自旋(1/2,1,3/2)Ising模型系統(tǒng)的相變行為進(jìn)行了研究,獲得了與EFT相符的結(jié)果。此外,當(dāng)增大參數(shù)L、Lc和Jcc,系統(tǒng)的相變溫度隨著L、Lc和Jcc的增大而增大。當(dāng)增大Lb和Jbb時(shí),系統(tǒng)的相變溫度幾乎沒有發(fā)生變化。
[Abstract]:With the development of science and technology, the research and development of layered magnetic materials have attracted much attention. Among them, there is compensation temperature in ferromagnetic materials, and compensation temperature has important application in magnetic recording. At the same time, the technology and means of synthesizing thin film materials are diversified, such as pulsed laser deposition, sol-gel, metal-organic vapor deposition, magnetron sputtering, etc., together with the breakthrough in theory and the practical application of science. Magnetic multilayer materials are entering a period of high tide development. For layered mixed spin materials, the Ising model of ferromagnetic double-layer mixed spin (1 ~ 2, 1), the Ising model of ferromagnetic three-layer mixed spin (1 ~ 2, 1, 3 ~ 2) and the Ising model of ferromagnetic three-layer mixed spin (1 ~ 2, 1, 3 ~ 2) have been established. The magnetic properties and thermodynamic properties of ferromagnetic and ferromagnetic Ising system are systematically studied by means of Monte Carlo method. The magnetic moment, magnetic susceptibility, internal energy and specific heat of the system are analyzed and discussed in terms of temperature, exchange coupling, thin film thickness and magnetic atomic concentration. The influence of compensation behavior and phase transition behavior. The exchange coupling effect and the effect of layer thickness on the magnetic and thermodynamic properties of the Ising model system with ferromagnetic bilayer spin (1 ~ 2, 1) have been studied. The results show that the phase transition temperature and compensation temperature of the system increase with the increase of intralayer exchange coupled Jbb. It is found that the smaller the Jbb is, the more likely the compensation behavior is. The competition between temperature and exchange coupling leads to the appearance of N, Q and P curves predicted by N 茅 el's theory. The increase of interlayer exchange coupling (Jab) has little effect on phase transition temperature and compensation temperature. With the increase of layer thickness, the phase transition temperature increases first and then does not change, and when L is small, the compensation temperature changes obviously. The exchange coupling of the Ising model system with three layers of ferromagnetic spin (1 ~ 2, 1, 3 ~ 2) is studied. The effects of layer thickness and atomic concentration on the magnetic and thermodynamic properties of the system are studied. The compensation behavior and phase transition behavior of the system are mainly studied. The results show that with the increase of Jbb, the compensation temperature has no effect, but the phase transition temperature increases. The larger the JCC, the more difficult the compensation temperature is. With the increase of layer thickness L, the compensation temperature does not change, but the phase transition temperature increases. The subgrid thickness Lb increases, the phase transition temperature increases, and the compensation temperature disappears, indicating that the larger the Lb is, the more difficult the compensation temperature will be. When the subgrid thickness Lc increases, the phase transition temperature does not change, and the compensation temperature increases first and then the compensation temperature does not change. Changing the atomic concentration P of the system, it is found in the phase diagram that there is a double compensation point in the system. In order to compare with the theoretical results of the correlation effective field (EFT), the phase transition behavior of the ferromagnetic three-layer mixed spin (1? 2, 1, 3? 2) Ising model is studied, and the results are in agreement with those of EFT. In addition, when the parameter L is increased, the phase transition temperature of LC and Jcc, systems increases with the increase of L, LC and Jcc. When Lb and Jbb are increased, the phase transition temperature of the system is almost unchanged.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O469

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