本文選題：鈷鎂 + 顆粒��； 參考：《南京大學(xué)》2014年博士論文

【摘要】：近年來(lái),隨著科學(xué)技術(shù)的發(fā)展,人們要求提高信息存儲(chǔ)密度,縮小存儲(chǔ)器件尺寸。存儲(chǔ)器件中磁性顆粒的尺寸縮小,有利于提高存儲(chǔ)密度,但是當(dāng)磁性顆粒的大小逐漸減小到臨界值以下時(shí),磁性顆粒內(nèi)的磁矩會(huì)變得無(wú)序,這就是所謂的"超順磁性限制",因此,找到有效穩(wěn)定磁矩的辦法,這對(duì)于基礎(chǔ)研究和技術(shù)應(yīng)用都很有意義。引入交換偏置效應(yīng)是解決這個(gè)問(wèn)題的可能辦法之一。1956年,Meikleijohn和Bean在部分被氧化的Co顆粒系統(tǒng)中觀察到交換偏置效應(yīng)。此后,交換偏置效應(yīng)在多種人造材料中被觀察到,科學(xué)家們對(duì)交換偏置現(xiàn)象做了很多深入的探索。2003年,Shumryev等在《Nature》上撰文提出,可以利用Co/CoO顆粒中的交換偏置效應(yīng)打破納米Co顆粒的超順磁性限制,提高Co顆粒的熱穩(wěn)定性,并且增大矯頑力。這一研究成果為交換偏置效應(yīng)帶來(lái)了新的應(yīng)用價(jià)值,因此引起了人們的廣泛興趣。弄清交換偏置效應(yīng)產(chǎn)生的微觀機(jī)制并用恰當(dāng)?shù)睦碚摷右越忉?再據(jù)此設(shè)計(jì)制造能獲得高交換偏置場(chǎng)的人造材料,是目前這一領(lǐng)域的研究重點(diǎn)。但是令人遺憾的是迄今為止交換偏置效應(yīng)產(chǎn)生的確切微觀機(jī)制仍然不明確,已有的多種理論模型也仍然存在爭(zhēng)議。有一種理論認(rèn)為交換偏置效應(yīng)與鐵磁和反鐵磁界面的自旋結(jié)構(gòu)有關(guān),在鐵磁和反鐵磁界面處不隨外加磁場(chǎng)旋轉(zhuǎn)的未補(bǔ)償自旋是交換偏置效應(yīng)的真正來(lái)源,交換偏置場(chǎng)的大小與這種未補(bǔ)償自旋的密度高低有關(guān)。目前,這種觀點(diǎn)被比較廣泛地接受,并且正在被越來(lái)越多的實(shí)驗(yàn)結(jié)果證實(shí)。根據(jù)交換偏置效應(yīng)的特征,結(jié)合磁性顆粒膜的性質(zhì),我們制備了一系列Co/CoO-MgO顆粒膜樣品(Co/CoO顆粒嵌入MgO介質(zhì))。本文研究的重點(diǎn):1.利用磁性表征技術(shù)測(cè)量這一系列Co/CoO-MgO顆粒膜樣品的磁、電參數(shù)(交換偏置場(chǎng)、矯頑力、磁疇結(jié)構(gòu)、電阻等);2.利用X射線磁性圓二色性(XMCD)實(shí)驗(yàn)確定Co與CoO界面處的自旋結(jié)構(gòu);3.根據(jù)實(shí)驗(yàn)結(jié)果探究該系統(tǒng)具有大交換偏置場(chǎng)和大矯頑力的原因,證明交換偏置的未補(bǔ)償自旋模型理論的合理性;4.明確交換偏置場(chǎng)和矯頑力之間的關(guān)系,找到調(diào)控交換偏置場(chǎng)和矯頑力的可能途徑,以利于研發(fā)高性能的磁記錄材料。5.測(cè)試發(fā)現(xiàn)樣品具有顯著的磁光效應(yīng)增強(qiáng),這是樣品中的金屬鈷顆粒表面的局域表面等離激元共振引起的。論文主要包括以下三個(gè)部分:一、(Co/CoO)-MgO顆粒膜中的交換偏置效應(yīng)的研究1、利用磁控濺射技術(shù)制作了一系列組份不同的Co/CoO-MgO顆粒膜樣品。選取鈷原子比為69%的樣品Co69Mg7024(即CCMO1)和鉆原子比為80%的樣品Co80Mg6014(即CCM02)做了仔細(xì)的研究。2、在滲流閾值以下的樣品CCMO1中觀察到高達(dá)2460Oe的交換偏置場(chǎng)和高達(dá)62000e的矯頑力。在Co的L2,3測(cè)得的x射線磁圓二色性吸收譜清楚地表明鐵磁信號(hào)部分來(lái)源于通常呈反鐵磁性的CoO殼層。3、研究結(jié)果證實(shí)了未補(bǔ)償自旋模型的正確性,而且進(jìn)一步證實(shí)了被釘軋的未補(bǔ)償自旋的數(shù)量影響交換偏置場(chǎng),可旋轉(zhuǎn)的未補(bǔ)償自旋的數(shù)量影響矯頑力。我們觀察到的來(lái)源于反鐵磁CoO殼層的鐵磁XMCD信號(hào)就清楚地證明了后者的存在。二、(Co/CoO)-MgO顆粒膜中的巨矯頑力研究1、借助于高分辨透射電子顯微鏡(HRTEM)圖片,我們清楚地確定了樣品Co56/(CoO)32-(MgO)12和 Co75/(CoO)15-(MgO)10 的形態(tài)和結(jié)構(gòu)。2、借助于原子力顯微鏡(AFM)和磁力顯微鏡(MFM)技術(shù),我們弄清了樣品Co56/(CoO)32-(MgO)12和 Co75/(CoO)15-(MgO)10的形貌和疇結(jié)構(gòu),并進(jìn)行了對(duì)比。3、通過(guò)分析Co/CoO-MgO納米顆粒膜樣品的磁滯回線,我們得到了樣品Co56/(CoO)32-(MgO)12和Co75/(CoO)15-(MgO)10在相同條件下交換偏置場(chǎng)和矯頑力之間的差異,以及兩個(gè)樣品交換偏置場(chǎng)和矯頑力隨溫度變化的情況。我們還特別測(cè)量了外加不同大小冷卻磁場(chǎng)時(shí)樣品Co56/(CoO)32-(MgO)12的交換偏置場(chǎng)和矯頑力。4、通過(guò)對(duì)樣品Co56/(CoO)32-(MgO)12和Co75/(CoO)15-(MgO)10的磁性分析可得,鈷體積比恰好達(dá)到滲流閾值的樣品Co56/(CoO)32-(MgO)12具有高達(dá)7121 Oe的矯頑力和高達(dá)3435 Oe的交換偏置場(chǎng)�？梢�(jiàn)交換偏置的存在有利于提高系統(tǒng)的矯頑力。5、研究結(jié)果表明,通過(guò)改變Co/CoO-MgO納米顆粒的交換偏置場(chǎng)的大小可以調(diào)控其矯頑力。三、(Co/CoO)-MgO顆粒膜中的克爾效應(yīng)研究1、測(cè)量得出Co/CoO-MgO顆粒膜的磁光克爾角與入射光波長(zhǎng)之間的關(guān)系曲線。應(yīng)用經(jīng)典4×4矩陣法擬合了Co/CoO-MgO顆粒膜的磁光克爾角與入射光波長(zhǎng)之間關(guān)系的實(shí)驗(yàn)曲線。2、測(cè)量了入射光波長(zhǎng)為共振波長(zhǎng)時(shí)所有樣品的磁光克爾角。3、用等離激元理論解釋了樣品中磁光克爾角增大的原因。
[Abstract]:In recent years, with the development of science and technology, people need to improve the density of the information storage and reduce the size of the memory parts. The size of the magnetic particles in the memory parts is reduced, which is beneficial to the increase of the storage density. But when the size of the magnetic particles gradually decreases below the critical value, the magnetic moments in the magnetic particles will become disordered. This is called "super". Paramagnetic confinement, therefore, it is significant for both basic and technical applications to find effective stable magnetic moments. The introduction of the exchange bias effect is one of the possible solutions to this problem in.1956, and Meikleijohn and Bean observe the exchange bias effect in the partially oxidized Co particle system. A variety of artificial materials have been observed, scientists have made a lot of in-depth exploration on the phenomenon of exchange bias in.2003 years. Shumryev and other articles on suggest that the exchange bias effect in Co/CoO particles can be used to break the superparamagnetic limit of nano Co particles, improve the thermal stability of Co particles, and increase the coercivity. Because of its new application value for the exchange bias effect, it has aroused wide interest. It is a major focus in this field to make clear the microscopic mechanism of the exchange bias effect and to explain it with appropriate theory, and then to design and manufacture artificial materials that can obtain high exchange bias field. So far the exact microscopic mechanism of the exchange bias effect is still unclear, and many theoretical models are still controversial. One theory is that the exchange bias effect is related to the spin structure of the ferromagnetic and antiferromagnetic interfaces, and the uncompensated spin at the ferromagnetic and antiferromagnetic interfaces that do not rotate with the magnetic field is the exchange bias effect. The real source, the size of the exchange bias field is related to the density of this uncompensated spin. At present, this view is widely accepted and is being confirmed by more and more experimental results. Based on the characteristics of the exchange bias effect and the properties of magnetic granular films, we have prepared a series of Co/CoO-MgO granular film samples (Co/Co O particles are embedded in the MgO medium. The focus of this paper is: 1. using magnetic characterization techniques to measure the magnetic, electrical parameters (exchange bias field, coercive force, domain structure, resistance and so on) of this series of Co/CoO-MgO particles; 2. using X ray magnetic circle two color (XMCD) experiment to determine the spin structure at the interface between Co and CoO; 3. explore the system based on the experimental results. The reasons for the large exchange bias field and the large coercivity are proved, and the reasonableness of the theory of the uncompensated spin model for the exchange bias is proved. 4. the relationship between the exchange bias field and the coercive force is clearly defined, and the possible way to regulate the exchange bias field and coercive force is found to facilitate the development of the high performance magnetic recording material.5. test discovery sample. The magneto optic effect is enhanced, which is caused by the local surface plasmon resonance on the surface of the metal cobalt particles in the sample. The thesis mainly includes the following three parts: (1) a study of the exchange bias effect in (Co/CoO) -MgO granular film. A series of different Co/CoO-MgO particle films were fabricated by magnetron sputtering. A careful study of the 69% sample Co69Mg7024 (CCMO1) and the sample Co80Mg6014 (CCM02) of the drill atomic ratio (CCM02) was carefully studied. The exchange bias field of up to 2460Oe and the coercive force of up to 62000e were observed in the sample CCMO1 below the threshold of the percolation threshold. The ferromagnetic signal part of the X ray magnetic circle two color absorption spectrum measured in Co L2,3 was clear. The results from the CoO shell.3, usually antiferromagnetic, confirm the correctness of the uncompensated spin model and further confirm the effect of the number of uncompensated spins on the exchange bias field, and the number of rotatable uncompensated spin affects the coercive force. The ferromagnetic XMCD signal from the antiferromagnetic CoO shell is observed. The existence of the latter is clearly demonstrated. Two, the giant coercive force in the granular film of (Co/CoO) -MgO is 1. With the help of high resolution transmission electron microscopy (HRTEM) images, we have clearly identified the morphology and structure.2 of the samples Co56/ (CoO) 32- (MgO) 12 and Co75/ (CoO) 15- (MgO) 10, with the aid of atomic force microscopy and magnetic force microscopy. We have made clear the morphology and domain structure of the samples Co56/ (CoO) 32- (MgO) 12 and Co75/ (CoO) 15- (MgO) 10, and compared the.3. By analyzing the hysteresis loop of the Co/CoO-MgO nanoparticle film samples, we obtained the difference between the exchange bias field and the coercive force of the sample Co56/ (CoO) 12 and 10. We also measured the exchange bias field and coercive force.4 of the sample Co56/ (CoO) 32- (MgO) 12 added with different sizes of cooling magnetic field, and the cobalt volume ratio was right to the percolation threshold by the magnetic analysis of the sample Co56/ (CoO) 32- (MgO) 12 and Co75/ (CoO) 15- (MgO) 10. The sample Co56/ (CoO) 32- (MgO) 12 has a coercivity of up to 7121 Oe and a exchange bias field with up to 3435 Oe. The existence of the exchange bias is beneficial to improve the coercive force.5 of the system. The results show that the coercive force can be regulated by changing the exchange bias field of Co/CoO-MgO nanoparticles. The Kerr in three, (Co/CoO) -MgO particle film can be controlled. The relationship between the magneto-optical Kerr angle of the Co/CoO-MgO particle film and the wavelength of the incident light is measured. The experimental curve.2 of the relation between the magnetic light Kerr angle of the Co/CoO-MgO particle film and the incident light wavelength is fitted by the classical 4 x 4 matrix method. The magneto-optical Kerr angle.3 of all samples when the incident light wave length is the resonant wavelength is measured. The reason for the increase of the magneto optical Kerr angle in the sample is explained by the plasmon theory.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：O484.43

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