【摘要】：隨著半導體科技的進步,個人電腦和智能終端產(chǎn)品的普及,人們對于信息存儲的需求日益增大,因此關于超高存儲密度的磁性存儲材料出現(xiàn)了飛速的進步。為了提高磁性存儲器件的存儲密度,必須減小每一個磁性記錄單元的尺寸大小,而尺寸減小所帶來的過小的磁晶各向異性能(MAE)往往無法克服室溫的熱擾動,導致存儲器件在使用過程中丟失信息數(shù)據(jù)。為了克服超順磁現(xiàn)象的影響,高磁晶各向異性能的材料被提上了研究方案,但是過高的磁晶各向異性能會帶來高的矯頑力,導致信息數(shù)據(jù)在寫入存儲器的過程變得非常困難。因此尋找具有合適磁晶各向異性能的磁性材料是當前磁性存儲器發(fā)展的關鍵,并且如果能夠?qū)τ涗泦卧拇啪Ц飨虍愋阅苓M行切實有效的調(diào)控,將會大大減低磁性記錄材料的尋找難度,提高材料的利用價值。近年來,為了尋找具有合適磁晶各向異性能的磁性存儲材料,人們在實驗和理論上都進行了許多探索。研究發(fā)現(xiàn),由于低維結(jié)構本身的各向異性,將過渡金屬原子與低維體系結(jié)合往往可以帶來較高的磁晶各向異性能。在本文中,我們利用基于密度泛函理論的綴加平面波方法軟件包,通過多種過渡金屬原子來修飾二維酞菁片層結(jié)構,研究體系的磁學性質(zhì)。我們發(fā)現(xiàn)5d金屬由于較高的自旋軌道耦合系數(shù)(SOC),使得修飾后的5d-Pc網(wǎng)格表現(xiàn)出較高的各向異性。且體系的磁晶各向異性能對金屬原子d軌道的能級排布密切相關。以此為基礎,我們通過引入O原子對金屬原子的d軌道進行重排,提出了全新的軌道調(diào)控的方法,期望能夠?qū)π滦痛判源鎯Σ牧系脑O計提供一定的指導作用。我們的計算結(jié)構表明,當O原子吸附在金屬原子上方,形成的O-MPc結(jié)構的金屬原子軌道發(fā)生重排,而通過電場控制O原子的高度可以對d電子的能級進行精準的調(diào)控,從而可以直接控制體系的磁晶各向異性能。通過對比,發(fā)現(xiàn)這種調(diào)控方式更為直接有效,且調(diào)控范圍遠遠高于傳統(tǒng)調(diào)控手段。我們進一步通過鹵素原子替代O原子進行了調(diào)控,證明了控制非金屬原子與金屬原子之間的相互作用大小就可以精準的控制能級排布,實現(xiàn)對磁晶各向異性能的有效調(diào)控。我們利用已有的研究手段和新型的調(diào)控方法探索了新型的金屬有機框架結(jié)構(MOF),雖然這種新型的材料并沒有表達出令人滿意的磁學性質(zhì),但充分證明了d電子的軌道調(diào)控可以實現(xiàn)對體系磁晶各向異性能的大幅度控制。
[Abstract]:With the development of semiconductor technology and the popularity of personal computers and intelligent terminal products, the demand for information storage is increasing. Therefore, magnetic storage materials with ultra-high storage density have made rapid progress. In order to improve the storage density of magnetic memory devices, the size of each magnetic recording unit must be reduced, and the small magnetocrystalline anisotropy energy (MAE) can not overcome the thermal disturbance at room temperature. Causes the memory device to lose information data during use. In order to overcome the influence of superparamagnetism, the materials with high magnetocrystalline anisotropy energy have been proposed. However, the high magnetocrystalline anisotropy energy will lead to high coercivity, which makes it very difficult for information data to be written to the memory. Therefore, finding magnetic materials with appropriate magnetocrystalline anisotropy energy is the key to the development of magnetic memory, and if the magnetocrystalline anisotropy energy of the recording unit can be effectively regulated, It will greatly reduce the difficulty of finding magnetic recording materials and improve the utilization value of the materials. In recent years, in order to find magnetic storage materials with suitable magnetocrystalline anisotropic energy, many experiments and theories have been carried out. It is found that due to the anisotropy of the low-dimensional structure, the combination of transition metal atoms with low-dimensional systems often leads to higher magnetocrystalline anisotropy energy. In this paper, we study the magnetic properties of the system by modifying the two-dimensional phthalocyanine lamellar structure with a variety of transition metal atoms by using the density functional theory (DFT) based affixed plane wave method software package. We find that the modified 5d-Pc meshes exhibit high anisotropy due to the high spin-orbit coupling coefficient (SOC),) of 5d metals. The magnetocrystalline anisotropy energy of the system is closely related to the arrangement of the energy levels of the d orbitals of the metal atoms. On this basis, by introducing O atoms to rearrange the d orbitals of metal atoms, a new orbital control method is proposed, which is expected to provide some guidance for the design of new magnetic storage materials. Our computational structure shows that when O atoms are adsorbed on metal atoms, the metal atom orbitals of the O-MPc structure are rearranged, and the energy levels of d electrons can be precisely regulated by controlling the height of O atoms by an electric field. Thus the magnetocrystalline anisotropy energy of the system can be directly controlled. Through comparison, it is found that this regulation method is more direct and effective, and the range of regulation is much higher than that of traditional control means. We further control the energy levels by replacing O atoms with halogen atoms. It is proved that by controlling the interaction between nonmetallic atoms and metal atoms, we can precisely control the distribution of energy levels and realize the effective regulation of magnetocrystalline anisotropic energy. We have explored a new metal-organic frame structure, (MOF), using existing research tools and new regulatory methods, although this new material has not shown satisfactory magnetic properties. However, it is fully proved that the orbital control of d electrons can control the anisotropic energy of magnetocrystalline system greatly.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP333;O482.5

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