co系钙钛矿材料中的磁性分析word格式论文.docxVIP

of an enlarged double cell. We find that the ground state of the CeCoO3 is the high-spin antiferromagnetically ordered state for given prameters.Next, we investigate the spin-state transition in the Ce-doped SrCoO3. From the configuration of the Co4+ions, we obtain the new three possible states: the low-spinstate（LS,t5 e2 x ）, the intermediate-spin state（IS,t4+xe1+x ）and the high-spin state2 g g2 gg2 gg（HS, t3+2 xe2 ）as well as their combinations on the doubled cell are taken as theinitial configurations. It is found that with doping, the number of the iterant eg electrons decreases while the t2 g electrons remain localized. Our results suggest that the metals here are all half-metals in the whole doping and become insulator inthe last. When doping concentration crosses x=0.2, the IS state is replaced by the LS-IS -FM state. As doping increases further, IS Co ions are replaced by the HS ions with the same moment direction for 0.38≤x＜0.79, the LS–HS FM state is the ground state. When 0.79≤x＜0.9, the IS-CAFM state becomes the ground state of the system. The insulator-metal transition occurs in the region, 0.9＜x≤1.0, the groundstate of the system becomes IS-GAFM state, and it is a insulator. In fact, when x=1.0, here the intermediate-spin nearest-neighbor antiferromagnetically ordered state is the HS-HS-AFM state in the compound CeCoO3, especially the enhancing Co-d character at the top of the valence band with the doping concentration, and O-p character at the bottom of the valence band.Keywords: Hartree-Fock approximation, Co perovskites, Spin state, Magnetic ground state, Density of state, Doping concentration独创性声明本人声明所呈交的论文是我个人在导师指导下进行的研究工作 及取得的研究成果。尽我所知，除了文中特别加以标注和致谢的地方 外，论文中不包括其他人已经发表或撰写过的研究成果，也不包含为 获得西北师范大学或其他教育机构的学位或证书而使用过的材料。与 我一同工作的同志对本研究所做的任何贡献均已在论文中作了明确 的说明并表示了谢意。签名：日期： 关于论文使用授权的说明本人完全了解西北师范大学有关保留、使用学位论文的规定，即: 学校有权保留送交论文的复印件，允许论文被查阅和借阅;学校可以 公布论文的全部或部分内容，可以采用影印、缩印或其他复制手段保 存论文。（必威体育官网网址的论文在解密后应遵守此规定）签名：导师签名：日期： 第一章 绪论钙钛矿掺杂稀土锰氧化物由于具有超巨磁电阻效应（colossa